Convert HTML to PDF in .NET Core using C# with IronPDF

Jacob Mellor

Updated: September 17, 2026

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Generating high-fidelity PDFs directly from HTML is a routine requirement in modern .NET applications: reports, invoices, and tickets all need pixel-perfect output that matches the web UI. IronPDF simplifies this workflow by exposing a single C# API for rendering HTML, Razor views, and full websites into standards-compliant PDF documents. By the end of this guide a developer will be able to convert URLs, raw HTML, or MVC views in an ASP.NET Core project, and deploy the same code to Windows, Linux, Docker, or serverless environments.

Effortlessly convert HTML to PDF in .NET Core using the IronPDF library. This guide provides a simple example to get you started quickly by rendering HTML content into a high-quality PDF with minimal code. Perfect for developers looking to integrate PDF creation into their applications with ease.

Quick-Start Checklist

1. Install - Install-Package IronPdf
2. Render a URL - ChromePdfRenderer.RenderUrlAsPdf()
3. Render raw HTML - ChromePdfRenderer.RenderHtmlAsPdf()
4. Export a Razor view - ChromePdfRenderer.RenderHtmlAsPdfAsync()
5. Fine-tune output - leverage ChromePdfRenderer.RenderingOptions

What This Tutorial Covers

• URL, HTML string, and Razor view conversion
• Paper, margin, and media-type configuration
• Cross-platform deployment (Windows, Linux, Docker)
• Post-processing: merge, watermark, password-protect, and digitally sign PDFs
• End-to-end sample: ticket-booking MVC app

How do I install the PDF library in .NET Core?

Installing the library is a one-liner in any .NET 8 project and remains forward-compatible with .NET 9 STS and .NET 10 LTS. Use NuGet's Package Manager Console and the package manager will resolve every dependency automatically for Windows, Linux, Docker, and serverless targets.

:ProductInstall            # .NET 8 LTS and higher

:ProductInstall            # .NET 8 LTS and higher

Once installed, confirm everything is wired up by converting any public URL:

public class ClientModel
{
    [Required]
    public string Name { get; set; }
    [Required]
    public string Phone { get; set; }
    [Required]
    public string Email { get; set; }
}

public class ClientModel
{
    [Required]
    public string Name { get; set; }
    [Required]
    public string Phone { get; set; }
    [Required]
    public string Email { get; set; }
}

Public Class ClientModel
	<Required>
	Public Property Name() As String
	<Required>
	Public Property Phone() As String
	<Required>
	Public Property Email() As String
End Class

Public Class ClientModel
	<Required>
	Public Property Name() As String
	<Required>
	Public Property Phone() As String
	<Required>
	Public Property Email() As String
End Class

How it works

• ChromePdfRenderer spins up a sandboxed Chromium instance under the hood; no separate Chrome install is required.
• RenderUrlAsPdf captures the fully rendered DOM, including JavaScript-driven content, CSS media queries, and fonts.
• The resulting PdfDocument exposes helper methods for merging, password-protecting, or digitally signing the output: capabilities covered later in this tutorial.

For more detail on deployment nuances (Azure App Service, AWS Lambda, on-prem Linux), see the dedicated installation guide and the advanced NuGet setup pages. Internal CI/CD tips for Docker and K8s clusters are covered in Docker deployment best practices.

How can a .NET Core service convert a live website URL to PDF?

A single call to RenderUrlAsPdf is enough: pass any publicly reachable URL and IronPDF returns a fully rendered, standards-compliant PDF. The code below targets .NET 8 LTS and compiles unchanged on .NET 9 STS as well as the forthcoming .NET 10 release in 2025.

Step-by-step example

public class ClientServices
{
    private static ClientModel _clientModel;
    public static void AddClient(ClientModel clientModel)
    {
        _clientModel = clientModel;
    }
    public static ClientModel GetClient()
    {
        return _clientModel;
    }
}

public class ClientServices
{
    private static ClientModel _clientModel;
    public static void AddClient(ClientModel clientModel)
    {
        _clientModel = clientModel;
    }
    public static ClientModel GetClient()
    {
        return _clientModel;
    }
}

Public Class ClientServices
	Private Shared _clientModel As ClientModel
	Public Shared Sub AddClient(ByVal clientModel As ClientModel)
		_clientModel = clientModel
	End Sub
	Public Shared Function GetClient() As ClientModel
		Return _clientModel
	End Function
End Class

Public Class ClientServices
	Private Shared _clientModel As ClientModel
	Public Shared Sub AddClient(ByVal clientModel As ClientModel)
		_clientModel = clientModel
	End Sub
	Public Shared Function GetClient() As ClientModel
		Return _clientModel
	End Function
End Class

Why it works

• ChromePdfRenderer spins up a sandboxed Chromium instance: no system Chrome dependency, keeping Docker images slim.
• RenderUrlAsPdf waits for the DOM and JavaScript to finish before snapshotting, so single-page apps render correctly.
• Setting CssMediaType to Print tells the engine to use print-specific rules, matching a browser's Print → Save as PDF output.
• The resulting PdfDocument can be encrypted, digitally signed, merged, or rasterized: capabilities covered in later sections.

Related resources

• API reference - ChromePdfRenderer.RenderUrlAsPdf
• API reference - PdfDocument.SaveAs
• Tutorial - Deploy IronPDF in Docker containers

How do I convert raw HTML into a PDF in .NET Core?

Passing an HTML string (or a Razor view’s rendered markup) to ChromePdfRenderer.RenderHtmlAsPdf instantly produces a standards-compliant PDF. The method spins up IronPDF’s embedded Chromium engine, so no external browser installation or WebView dependency is required. The same code shown below compiles on .NET 8 LTS today and remains forward-compatible with .NET 9 and the scheduled .NET 10 release in November 2025.

Example: generate a PDF from an HTML fragment

@model IronPdfMVCHelloWorld.Models.ClientModel
@{
  ViewBag.Title = "Book Ticket";
}
<h2>Index</h2>
@using (Html.BeginForm())
{
  <div class="form-horizontal">
    @Html.ValidationSummary(true, "", new { @class = "text-danger" })
    <div class="form-group">
      @Html.LabelFor(model => model.Name, htmlAttributes: new { @class = "control-label col-md-2" })
      <div class="col-md-10">
        @Html.EditorFor(model => model.Name, new { htmlAttributes = new { @class = "form-control" } })
        @Html.ValidationMessageFor(model => model.Name, "", new { @class = "text-danger" })
      </div>
    </div>
    <div class="form-group">
      @Html.LabelFor(model => model.Phone, htmlAttributes: new { @class = "control-label col-md-2" })
      <div class="col-md-10">
        @Html.EditorFor(model => model.Phone, new { htmlAttributes = new { @class = "form-control" } })
        @Html.ValidationMessageFor(model => model.Phone, "", new { @class = "text-danger" })
      </div>
    </div>
    <div class="form-group">
      @Html.LabelFor(model => model.Email, htmlAttributes: new { @class = "control-label col-md-2" })
      <div class="col-md-10">
        @Html.EditorFor(model => model.Email, new { htmlAttributes = new { @class = "form-control" } })
        @Html.ValidationMessageFor(model => model.Email, "", new { @class = "text-danger" })
      </div>
    </div>
    <div class="form-group">
      <div class="col-md-10 pull-right">
        <button type="submit" value="Save" class="btn btn-sm">
          <i class="fa fa-plus"></i>
          <span>
            Save
          </span>
        </button>
      </div>
    </div>
  </div>
}

@model IronPdfMVCHelloWorld.Models.ClientModel
@{
  ViewBag.Title = "Book Ticket";
}
<h2>Index</h2>
@using (Html.BeginForm())
{
  <div class="form-horizontal">
    @Html.ValidationSummary(true, "", new { @class = "text-danger" })
    <div class="form-group">
      @Html.LabelFor(model => model.Name, htmlAttributes: new { @class = "control-label col-md-2" })
      <div class="col-md-10">
        @Html.EditorFor(model => model.Name, new { htmlAttributes = new { @class = "form-control" } })
        @Html.ValidationMessageFor(model => model.Name, "", new { @class = "text-danger" })
      </div>
    </div>
    <div class="form-group">
      @Html.LabelFor(model => model.Phone, htmlAttributes: new { @class = "control-label col-md-2" })
      <div class="col-md-10">
        @Html.EditorFor(model => model.Phone, new { htmlAttributes = new { @class = "form-control" } })
        @Html.ValidationMessageFor(model => model.Phone, "", new { @class = "text-danger" })
      </div>
    </div>
    <div class="form-group">
      @Html.LabelFor(model => model.Email, htmlAttributes: new { @class = "control-label col-md-2" })
      <div class="col-md-10">
        @Html.EditorFor(model => model.Email, new { htmlAttributes = new { @class = "form-control" } })
        @Html.ValidationMessageFor(model => model.Email, "", new { @class = "text-danger" })
      </div>
    </div>
    <div class="form-group">
      <div class="col-md-10 pull-right">
        <button type="submit" value="Save" class="btn btn-sm">
          <i class="fa fa-plus"></i>
          <span>
            Save
          </span>
        </button>
      </div>
    </div>
  </div>
}

model ReadOnly Property () As IronPdfMVCHelloWorld.Models.ClientModel
  ViewBag.Title = "Book Ticket"
End Property
'INSTANT VB TODO TASK: The following line could not be converted:
(Of h2) Index</h2> [using](Html.BeginForm())
If True Then
'INSTANT VB TODO TASK: The following line uses invalid syntax:
'  <div class="form-horizontal"> @Html.ValidationSummary(True, "", New { @class = "text-danger" }) <div class="form-group"> @Html.LabelFor(model => model.Name, htmlAttributes: New { @class = "control-label col-md-2" }) <div class="col-md-10"> @Html.EditorFor(model => model.Name, New { htmlAttributes = New { @class = "form-control" } }) @Html.ValidationMessageFor(model => model.Name, "", New { @class = "text-danger" }) </div> </div> <div class="form-group"> @Html.LabelFor(model => model.Phone, htmlAttributes: New { @class = "control-label col-md-2" }) <div class="col-md-10"> @Html.EditorFor(model => model.Phone, New { htmlAttributes = New { @class = "form-control" } }) @Html.ValidationMessageFor(model => model.Phone, "", New { @class = "text-danger" }) </div> </div> <div class="form-group"> @Html.LabelFor(model => model.Email, htmlAttributes: New { @class = "control-label col-md-2" }) <div class="col-md-10"> @Html.EditorFor(model => model.Email, New { htmlAttributes = New { @class = "form-control" } }) @Html.ValidationMessageFor(model => model.Email, "", New { @class = "text-danger" }) </div> </div> <div class="form-group"> <div class="col-md-10 pull-right"> <button type="submit" value="Save" class="btn btn-sm"> <i class="fa fa-plus"></i> <span> Save </span> </button> </div> </div> </div> }

model ReadOnly Property () As IronPdfMVCHelloWorld.Models.ClientModel
  ViewBag.Title = "Book Ticket"
End Property
'INSTANT VB TODO TASK: The following line could not be converted:
(Of h2) Index</h2> [using](Html.BeginForm())
If True Then
'INSTANT VB TODO TASK: The following line uses invalid syntax:
'  <div class="form-horizontal"> @Html.ValidationSummary(True, "", New { @class = "text-danger" }) <div class="form-group"> @Html.LabelFor(model => model.Name, htmlAttributes: New { @class = "control-label col-md-2" }) <div class="col-md-10"> @Html.EditorFor(model => model.Name, New { htmlAttributes = New { @class = "form-control" } }) @Html.ValidationMessageFor(model => model.Name, "", New { @class = "text-danger" }) </div> </div> <div class="form-group"> @Html.LabelFor(model => model.Phone, htmlAttributes: New { @class = "control-label col-md-2" }) <div class="col-md-10"> @Html.EditorFor(model => model.Phone, New { htmlAttributes = New { @class = "form-control" } }) @Html.ValidationMessageFor(model => model.Phone, "", New { @class = "text-danger" }) </div> </div> <div class="form-group"> @Html.LabelFor(model => model.Email, htmlAttributes: New { @class = "control-label col-md-2" }) <div class="col-md-10"> @Html.EditorFor(model => model.Email, New { htmlAttributes = New { @class = "form-control" } }) @Html.ValidationMessageFor(model => model.Email, "", New { @class = "text-danger" }) </div> </div> <div class="form-group"> <div class="col-md-10 pull-right"> <button type="submit" value="Save" class="btn btn-sm"> <i class="fa fa-plus"></i> <span> Save </span> </button> </div> </div> </div> }

What the code demonstrates

• Embedded Chromium: IronPDF bundles the Chromium engine, guaranteeing HTML5, CSS3, and JavaScript parity with modern browsers.
• Single dependency: A lightweight NuGet install covers Windows, Linux, Docker, and Azure/AWS without extra system libraries.
• Rendering options: PaperSize, CssMediaType, and RenderDelay mirror browser print settings so PDFs match on-screen layouts.
• Future-proof targeting: The API surface is the same across .NET 8, .NET 9 STS, and the upcoming .NET 10, so long-term maintenance is minimal.
• Post-processing hooks: PdfDocument exposes helpers for merging, password protection, and digital signatures, each covered later in this guide.

Further reading: see the step-by-step HTML-string-to-PDF tutorial and the full ChromePdfRenderer API documentation.

How can an ASP .NET Core MVC view be exported to PDF?

IronPDF renders a fully-processed Razor view ( .cshtml ) the same way a browser would and streams the result as a PdfDocument. The workflow below keeps controller logic clean, requires no browser plugins, and works on .NET 8 LTS, .NET 9 STS, and the scheduled .NET 10 release in November 2025.

End-to-end controller example

// TicketsController.cs - .NET 8 LTS / MVC
using IronPdf;
using Microsoft.AspNetCore.Mvc;
using YourApp.Models;           // TicketViewModel

public class TicketsController : Controller
{
    private readonly ChromePdfRenderer _renderer;

    public TicketsController()
    {
        _renderer = new ChromePdfRenderer
        {
            RenderingOptions =
            {
                PaperSize        = PdfPaperSize.A5,            // Compact ticket size
                PaperOrientation = PdfPaperOrientation.Portrait,
                FitToPaperMode   = IronPdf.Engines.Chrome.FitToPaperModes.AutomaticFit,
                CssMediaType     = PdfCssMediaType.Print,
                MarginTop = 5, MarginBottom = 10, MarginLeft = 5, MarginRight = 10   // mm
            }
        };
    }

    // GET /Tickets/Print/42
    public async Task<IActionResult> Print(int id)
    {
        TicketViewModel vm = await _service.GetTicketAsync(id);

        // 1. Render the Razor view to an HTML string
        string html  = await RazorTemplateEngine.RenderViewAsync(
                           HttpContext, "~/Views/Tickets/Print.cshtml", vm);

        // 2. Convert HTML → PDF
        using PdfDocument pdf = _renderer.RenderHtmlAsPdf(html);

        // 3. Stream back as a file
        return File(pdf.BinaryData, "application/pdf",
                    $"ticket-{id}.pdf");
    }
}

// TicketsController.cs - .NET 8 LTS / MVC
using IronPdf;
using Microsoft.AspNetCore.Mvc;
using YourApp.Models;           // TicketViewModel

public class TicketsController : Controller
{
    private readonly ChromePdfRenderer _renderer;

    public TicketsController()
    {
        _renderer = new ChromePdfRenderer
        {
            RenderingOptions =
            {
                PaperSize        = PdfPaperSize.A5,            // Compact ticket size
                PaperOrientation = PdfPaperOrientation.Portrait,
                FitToPaperMode   = IronPdf.Engines.Chrome.FitToPaperModes.AutomaticFit,
                CssMediaType     = PdfCssMediaType.Print,
                MarginTop = 5, MarginBottom = 10, MarginLeft = 5, MarginRight = 10   // mm
            }
        };
    }

    // GET /Tickets/Print/42
    public async Task<IActionResult> Print(int id)
    {
        TicketViewModel vm = await _service.GetTicketAsync(id);

        // 1. Render the Razor view to an HTML string
        string html  = await RazorTemplateEngine.RenderViewAsync(
                           HttpContext, "~/Views/Tickets/Print.cshtml", vm);

        // 2. Convert HTML → PDF
        using PdfDocument pdf = _renderer.RenderHtmlAsPdf(html);

        // 3. Stream back as a file
        return File(pdf.BinaryData, "application/pdf",
                    $"ticket-{id}.pdf");
    }
}

Imports IronPdf
Imports Microsoft.AspNetCore.Mvc
Imports YourApp.Models ' TicketViewModel

Public Class TicketsController
    Inherits Controller

    Private ReadOnly _renderer As ChromePdfRenderer

    Public Sub New()
        _renderer = New ChromePdfRenderer With {
            .RenderingOptions = New ChromePdfRenderOptions With {
                .PaperSize = PdfPaperSize.A5, ' Compact ticket size
                .PaperOrientation = PdfPaperOrientation.Portrait,
                .FitToPaperMode = IronPdf.Engines.Chrome.FitToPaperModes.AutomaticFit,
                .CssMediaType = PdfCssMediaType.Print,
                .MarginTop = 5,
                .MarginBottom = 10,
                .MarginLeft = 5,
                .MarginRight = 10
            }
        }
    End Sub

    ' GET /Tickets/Print/42
    Public Async Function Print(id As Integer) As Task(Of IActionResult)
        Dim vm As TicketViewModel = Await _service.GetTicketAsync(id)

        ' 1. Render the Razor view to an HTML string
        Dim html As String = Await RazorTemplateEngine.RenderViewAsync(HttpContext, "~/Views/Tickets/Print.cshtml", vm)

        ' 2. Convert HTML → PDF
        Using pdf As PdfDocument = _renderer.RenderHtmlAsPdf(html)
            ' 3. Stream back as a file
            Return File(pdf.BinaryData, "application/pdf", $"ticket-{id}.pdf")
        End Using
    End Function
End Class

Imports IronPdf
Imports Microsoft.AspNetCore.Mvc
Imports YourApp.Models ' TicketViewModel

Public Class TicketsController
    Inherits Controller

    Private ReadOnly _renderer As ChromePdfRenderer

    Public Sub New()
        _renderer = New ChromePdfRenderer With {
            .RenderingOptions = New ChromePdfRenderOptions With {
                .PaperSize = PdfPaperSize.A5, ' Compact ticket size
                .PaperOrientation = PdfPaperOrientation.Portrait,
                .FitToPaperMode = IronPdf.Engines.Chrome.FitToPaperModes.AutomaticFit,
                .CssMediaType = PdfCssMediaType.Print,
                .MarginTop = 5,
                .MarginBottom = 10,
                .MarginLeft = 5,
                .MarginRight = 10
            }
        }
    End Sub

    ' GET /Tickets/Print/42
    Public Async Function Print(id As Integer) As Task(Of IActionResult)
        Dim vm As TicketViewModel = Await _service.GetTicketAsync(id)

        ' 1. Render the Razor view to an HTML string
        Dim html As String = Await RazorTemplateEngine.RenderViewAsync(HttpContext, "~/Views/Tickets/Print.cshtml", vm)

        ' 2. Convert HTML → PDF
        Using pdf As PdfDocument = _renderer.RenderHtmlAsPdf(html)
            ' 3. Stream back as a file
            Return File(pdf.BinaryData, "application/pdf", $"ticket-{id}.pdf")
        End Using
    End Function
End Class

What this code illustrates

• No temporary files: the Razor view is rendered in-memory, then passed directly to RenderHtmlAsPdf, avoiding disk I/O and temp-folder race conditions.
• Ticket-sized output: PaperSize = A5 and narrow margins keep print-at-home tickets compact.
• Consistent print styles: CssMediaType = Print applies the same @media print CSS rules that browsers use.
• Binary streaming: pdf.BinaryData streams the document without touching the file-system; ideal for API endpoints and Lambda functions.
• Re-usable renderer: ChromePdfRenderer is instantiated once per controller, then reused, minimizing process-spawn overhead.

Next step: add encryption, digital signatures, or merge multiple tickets into a single file. See the merge example and the digital-signature how-to.

How can I fine-tune paper size, margins, headers, watermarks, and security before rendering?

IronPDF exposes a single ChromePdfRenderOptions object that controls every aspect of the output (paper dimensions, orientation, headers & footers, JavaScript timing, watermarks, encryption, and digital signatures), all without extra browser plugins.

Code sample: apply multiple options at once

[HttpPost]
public ActionResult Index(ClientModel model)
{
    if (ModelState.IsValid)
    {
        ClientServices.AddClient(model);
        return RedirectToAction("TicketView");
    }
  return View(model);
}

[HttpPost]
public ActionResult Index(ClientModel model)
{
    if (ModelState.IsValid)
    {
        ClientServices.AddClient(model);
        return RedirectToAction("TicketView");
    }
  return View(model);
}

<HttpPost>
Public Function Index(ByVal model As ClientModel) As ActionResult
	If ModelState.IsValid Then
		ClientServices.AddClient(model)
		Return RedirectToAction("TicketView")
	End If
  Return View(model)
End Function

<HttpPost>
Public Function Index(ByVal model As ClientModel) As ActionResult
	If ModelState.IsValid Then
		ClientServices.AddClient(model)
		Return RedirectToAction("TicketView")
	End If
  Return View(model)
End Function

Why these options matter

• PaperSize, Margins, and CssMediaType mirror a browser's print dialog so on-screen layouts and the PDF remain identical on Windows, Linux, and Docker.
• HTML headers and footers support Razor tokens, CSS, and JavaScript, handy for dynamic page numbers or branding.
• ApplyStamp lets a single line create branded watermarks with full HTML + CSS control.
• Security options enable 128-bit RC4 encryption, owner/user passwords, and granular permissions without third-party tools.
• Digital signatures add a cryptographic seal directly in code, maintaining legal authenticity and tamper evidence.
• Extraction helpers such as ExtractAllText and ExtractAllImages reverse the process when analysis is required.

Quick reference: Popular settings

Next tasks: merge multiple PDFs, extract text & images, and deploy to Docker or serverless. Continue to the deployment section to ensure cross-platform parity.

How can I deploy PDF-generation code to Docker on Linux and Windows?

IronPdf ships as a single self-contained NuGet package, so containerizing an ASP.NET Core (or console) app is straightforward on both Windows and Linux. The key is to copy the published binaries into a slim runtime image and, on Linux, add the two native libraries IronPDF requires (libnss3 and libatk1.0-0).

Multi-stage Dockerfile (Ubuntu 22.04)

####### ---------- stage 1 ----------
FROM mcr.microsoft.com/dotnet/sdk:8.0 AS build
WORKDIR /src
COPY ["MyPdfApp.csproj", "."]
RUN dotnet restore

COPY . .
RUN dotnet publish -c Release -o /app/publish

####### ---------- stage 2 ----------
FROM mcr.microsoft.com/dotnet/aspnet:8.0-jammy
######## Install two native libs required by Chromium
RUN apt-get update && \
    apt-get install -y --no-install-recommends libnss3 libatk1.0-0 && \
    rm -rf /var/lib/apt/lists/*

WORKDIR /app
COPY --from=build /app/publish .
ENTRYPOINT ["dotnet", "MyPdfApp.dll"]

####### ---------- stage 1 ----------
FROM mcr.microsoft.com/dotnet/sdk:8.0 AS build
WORKDIR /src
COPY ["MyPdfApp.csproj", "."]
RUN dotnet restore

COPY . .
RUN dotnet publish -c Release -o /app/publish

####### ---------- stage 2 ----------
FROM mcr.microsoft.com/dotnet/aspnet:8.0-jammy
######## Install two native libs required by Chromium
RUN apt-get update && \
    apt-get install -y --no-install-recommends libnss3 libatk1.0-0 && \
    rm -rf /var/lib/apt/lists/*

WORKDIR /app
COPY --from=build /app/publish .
ENTRYPOINT ["dotnet", "MyPdfApp.dll"]

End-to-end validation script

docker build -t pdf-demo .
docker run --rm -p 8080:80 pdf-demo
######### ↳ Navigate to http://localhost:8080/api/pdf?url=https://example.com

docker build -t pdf-demo .
docker run --rm -p 8080:80 pdf-demo
######### ↳ Navigate to http://localhost:8080/api/pdf?url=https://example.com

• The API action internally calls ChromePdfRenderer.RenderUrlAsPdf just like in Section2.
• IronPDF spins up its sandboxed Chromium process inside the container; no X server is required because it renders headlessly.
• Memory footprint stays modest even during large renders.

Internal resources

• Tutorial - Deploy IronPDF in Docker containers
• How-to - Run IronPDF on Azure App Service Linux
• API reference - ChromePdfRenderer class

My favorite library of this kind is IronPDF. It allows for fast and efficient manipulation of PDF files. It also has many valuable features, like exporting to PDF/A format and digitally signing PDF documents.

Milan Jovanovic

Microsoft MVP

View case study

IronOCR means we can save $40,000 annually from manual processing, while enhancing productivity and freeing up resources for high-impact tasks. I would highly recommend it.

Brent Matzelle

Chief Technology Officer, OPYN

View case study

How can I open, merge, watermark, and extract content from existing PDFs in .NET Core?

IronPDF treats every PDF (whether generated by IronPDF, Adobe® Acrobat, or third-party tools) as a first-class PdfDocument object that can be opened, edited, secured, and re-saved without quality loss. The same API surface works on .NET 8 LTS today and compiles unchanged on .NET 9 STS and the forthcoming .NET 10 release.

Unified sample: open → merge → watermark → extract

[HttpPost]
public ActionResult TicketView(TicketModel model)
{
    IronPdf.Installation.TempFolderPath = $@"{Directory.GetParent}/irontemp/";
    IronPdf.Installation.LinuxAndDockerDependenciesAutoConfig = true;
    var html = this.RenderViewAsync("_TicketPdf", model);
    var renderer = new IronPdf.ChromePdfRenderer();
    using var pdf = renderer.RenderHtmlAsPdf(html.Result, @"wwwroot/css");
    return File(pdf.Stream.ToArray(), "application/pdf");
}

[HttpPost]
public ActionResult TicketView(TicketModel model)
{
    IronPdf.Installation.TempFolderPath = $@"{Directory.GetParent}/irontemp/";
    IronPdf.Installation.LinuxAndDockerDependenciesAutoConfig = true;
    var html = this.RenderViewAsync("_TicketPdf", model);
    var renderer = new IronPdf.ChromePdfRenderer();
    using var pdf = renderer.RenderHtmlAsPdf(html.Result, @"wwwroot/css");
    return File(pdf.Stream.ToArray(), "application/pdf");
}

<HttpPost>
Public Function TicketView(ByVal model As TicketModel) As ActionResult
	IronPdf.Installation.TempFolderPath = $"{AddressOf Directory.GetParent}/irontemp/"
	IronPdf.Installation.LinuxAndDockerDependenciesAutoConfig = True
	Dim html = Me.RenderViewAsync("_TicketPdf", model)
	Dim renderer = New IronPdf.ChromePdfRenderer()
	Dim pdf = renderer.RenderHtmlAsPdf(html.Result, "wwwroot/css")
	Return File(pdf.Stream.ToArray(), "application/pdf")
End Function

<HttpPost>
Public Function TicketView(ByVal model As TicketModel) As ActionResult
	IronPdf.Installation.TempFolderPath = $"{AddressOf Directory.GetParent}/irontemp/"
	IronPdf.Installation.LinuxAndDockerDependenciesAutoConfig = True
	Dim html = Me.RenderViewAsync("_TicketPdf", model)
	Dim renderer = New IronPdf.ChromePdfRenderer()
	Dim pdf = renderer.RenderHtmlAsPdf(html.Result, "wwwroot/css")
	Return File(pdf.Stream.ToArray(), "application/pdf")
End Function

Why this matters

• Open & merge – PdfDocument.FromFile loads any standards-compliant PDF, including encrypted files, while PdfDocument.Merge concatenates an arbitrary number of documents in a single call.
• Watermark – ApplyStamp(new HtmlStamper(...)) embeds fully styled HTML/CSS overlays (logo, QR code, or diagonal text) on selected pages without rasterisation.
• Content extraction – ExtractAllText and ExtractAllImages pull raw UTF-8 text or binary image streams for downstream archiving or AI pipelines, while ExtractTextFromLayer scopes extraction to a named layer (OCG) in layered PDFs.
• Digital signatures ready – the same PdfDocument instance can be sealed by creating a PdfSignature and calling pdf.Sign(signature), producing RFC 3161-compliant hashes aligned with ISO 32000-2 digital-signature requirements.
• Open standard compliance – IronPDF preserves the original PDF structure (fonts, layers, XMP metadata) so the output remains compatible with Adobe® Reader and other ISO 32000-1 viewers.
• Future-proof – The API avoids interop assemblies and Win32 GDI calls, so code runs unchanged on Windows, Linux, Docker, and upcoming .NET 10 serverless SKUs.

Need split, rotate, or delete pages? See the page-level edit tutorial for granular operations.

How can PDFs be encrypted and digitally signed in .NET Core?

IronPDF secures a document in two steps: password-based encryption (user/owner passwords + granular permissions) and X.509 digital signatures that seal the file with a cryptographic hash. Both APIs live on the same PdfDocument object, so the workflow is identical on .NET 8 LTS today and compiles unchanged on .NET 9 STS and the forthcoming .NET 10 release.

Example: encrypt a document, lock print rights, and add a visible signature

using IronPdf;
using IronPdf.Signing;
using System.Drawing;

var renderer = new ChromePdfRenderer();
var pdf = renderer.RenderHtmlAsPdf("<h1>Confidential Report</h1>");

// Password-protect the document.
pdf.SecuritySettings.OwnerPassword = "owner-secret";
pdf.SecuritySettings.UserPassword = "user-secret";

// Lock print rights. An owner password is required for this to take effect.
pdf.SecuritySettings.AllowUserPrinting = IronPdf.Security.PdfPrintSecurity.NoPrint;

// Sign the document and stamp a visible signature image onto page 1.
var signature = new PdfSignature("cert123.pfx", "password")
{
    SigningContact = "support@ironsoftware.com",
    SigningLocation = "Chicago, USA",
    SigningReason = "Confidential Report Approval",
    SignatureImage = new PdfSignatureImage("IronSoftware.png", 0, new Rectangle(350, 750, 200, 100))
};
pdf.Sign(signature);

pdf.SaveAs("SecuredSignedReport.pdf");

using IronPdf;
using IronPdf.Signing;
using System.Drawing;

var renderer = new ChromePdfRenderer();
var pdf = renderer.RenderHtmlAsPdf("<h1>Confidential Report</h1>");

// Password-protect the document.
pdf.SecuritySettings.OwnerPassword = "owner-secret";
pdf.SecuritySettings.UserPassword = "user-secret";

// Lock print rights. An owner password is required for this to take effect.
pdf.SecuritySettings.AllowUserPrinting = IronPdf.Security.PdfPrintSecurity.NoPrint;

// Sign the document and stamp a visible signature image onto page 1.
var signature = new PdfSignature("cert123.pfx", "password")
{
    SigningContact = "support@ironsoftware.com",
    SigningLocation = "Chicago, USA",
    SigningReason = "Confidential Report Approval",
    SignatureImage = new PdfSignatureImage("IronSoftware.png", 0, new Rectangle(350, 750, 200, 100))
};
pdf.Sign(signature);

pdf.SaveAs("SecuredSignedReport.pdf");

Imports IronPdf
Imports IronPdf.Signing
Imports System.Drawing

Dim renderer = New ChromePdfRenderer()
Dim pdf = renderer.RenderHtmlAsPdf("<h1>Confidential Report</h1>")

' Password-protect the document.
pdf.SecuritySettings.OwnerPassword = "owner-secret"
pdf.SecuritySettings.UserPassword = "user-secret"

' Lock print rights. An owner password is required for this to take effect.
pdf.SecuritySettings.AllowUserPrinting = IronPdf.Security.PdfPrintSecurity.NoPrint

' Sign the document and stamp a visible signature image onto page 1.
Dim signature = New PdfSignature("cert123.pfx", "password") With {
    .SigningContact = "support@ironsoftware.com",
    .SigningLocation = "Chicago, USA",
    .SigningReason = "Confidential Report Approval",
    .SignatureImage = New PdfSignatureImage("IronSoftware.png", 0, New Rectangle(350, 750, 200, 100))
}
pdf.Sign(signature)

pdf.SaveAs("SecuredSignedReport.pdf")

Imports IronPdf
Imports IronPdf.Signing
Imports System.Drawing

Dim renderer = New ChromePdfRenderer()
Dim pdf = renderer.RenderHtmlAsPdf("<h1>Confidential Report</h1>")

' Password-protect the document.
pdf.SecuritySettings.OwnerPassword = "owner-secret"
pdf.SecuritySettings.UserPassword = "user-secret"

' Lock print rights. An owner password is required for this to take effect.
pdf.SecuritySettings.AllowUserPrinting = IronPdf.Security.PdfPrintSecurity.NoPrint

' Sign the document and stamp a visible signature image onto page 1.
Dim signature = New PdfSignature("cert123.pfx", "password") With {
    .SigningContact = "support@ironsoftware.com",
    .SigningLocation = "Chicago, USA",
    .SigningReason = "Confidential Report Approval",
    .SignatureImage = New PdfSignatureImage("IronSoftware.png", 0, New Rectangle(350, 750, 200, 100))
}
pdf.Sign(signature)

pdf.SaveAs("SecuredSignedReport.pdf")

Behind the scenes

• Password encryption: IronPDF encrypts the document with 128-bit RC4, blocking unauthorized opening, printing, or copy-paste.
• Permissions granularity: properties such as AllowUserPrinting and AllowUserFormData toggle per-action rights; an owner password is required for any restriction to take effect.
• Digital signatures: creating a PdfSignature and calling pdf.Sign(signature) embeds a certificate chain and a visible SignatureImage, creating tamper-evident hashes recognized by Adobe® Acrobat and other ISO 32000-2 viewers.
• One-stop API: both encryption and signing modify the same PdfDocument instance, avoiding multiple file passes and preserving internal fonts, layers, and metadata.

Core security settings

Internal resources for deeper dives

• Tutorial - Password-protect a PDF
• Example - Digitally sign a PDF
• API reference - PdfSecuritySettings

How can HTML-to-PDF performance be optimized and scaled in .NET Core?

IronPDF's Chromium engine already renders quickly on modern hardware, but throughput can be multiplied by batching renders, enabling multi-threading, and trimming Headless Chrome overhead. The tips below apply equally to all .NET versions.

1. Batch renders on a background thread pool

IronPdf.License.LicenseKey = "YourLicenseKey";
ChromePdfRenderer renderer = new ChromePdfRenderer();

// Set rendering options
renderer.RenderingOptions.PaperSize = IronPdf.Rendering.PdfPaperSize.A4;
renderer.RenderingOptions.PaperOrientation = IronPdf.Rendering.PdfPaperOrientation.Portrait;

renderer.RenderHtmlFileAsPdf(@"testFile.html").SaveAs("GeneratedFile.pdf");

IronPdf.License.LicenseKey = "YourLicenseKey";
ChromePdfRenderer renderer = new ChromePdfRenderer();

// Set rendering options
renderer.RenderingOptions.PaperSize = IronPdf.Rendering.PdfPaperSize.A4;
renderer.RenderingOptions.PaperOrientation = IronPdf.Rendering.PdfPaperOrientation.Portrait;

renderer.RenderHtmlFileAsPdf(@"testFile.html").SaveAs("GeneratedFile.pdf");

Imports IronPdf

License.LicenseKey = "YourLicenseKey"
Dim renderer As New ChromePdfRenderer()

' Set rendering options
renderer.RenderingOptions.PaperSize = Rendering.PdfPaperSize.A4
renderer.RenderingOptions.PaperOrientation = Rendering.PdfPaperOrientation.Portrait

renderer.RenderHtmlFileAsPdf("testFile.html").SaveAs("GeneratedFile.pdf")

Imports IronPdf

License.LicenseKey = "YourLicenseKey"
Dim renderer As New ChromePdfRenderer()

' Set rendering options
renderer.RenderingOptions.PaperSize = Rendering.PdfPaperSize.A4
renderer.RenderingOptions.PaperOrientation = Rendering.PdfPaperOrientation.Portrait

renderer.RenderHtmlFileAsPdf("testFile.html").SaveAs("GeneratedFile.pdf")

• ChromePdfRenderer is thread-safe; a single instance may serve dozens of concurrent tasks without deadlocks.
• Parallel.ForEach saturates every CPU core, improving throughput compared with a single-thread loop.
• If ASP.NET requests queue up, move heavy renders to a hosted background service or message queue to keep response times low.

2. Trim Headless Chrome startup cost

IronPDF ships its own Chromium build, but each render incurs a small startup tax. Pooling helps, and Linux containers must include two native libs:

RUN apt-get update && \
    apt-get install -y --no-install-recommends libnss3 libatk1.0-0

RUN apt-get update && \
    apt-get install -y --no-install-recommends libnss3 libatk1.0-0

Missing either library manifests as a libnss3.so not found error in Docker logs.

Recommended Chrome flags (automatically applied by IronPDF) include --disable-gpu and --no-sandbox to reduce memory and root-user issues in containers.

3. Wait for late JavaScript with RenderDelay or WaitFor

Pages that animate counters or fetch data after DOMContentLoaded may need a short delay:

renderer.RenderingOptions.RenderDelay = 200;        // ms
// OR: renderer.RenderingOptions.WaitFor.JavaScript("window.doneLoading === true");

renderer.RenderingOptions.RenderDelay = 200;        // ms
// OR: renderer.RenderingOptions.WaitFor.JavaScript("window.doneLoading === true");

renderer.RenderingOptions.RenderDelay = 200 ' ms
' OR: renderer.RenderingOptions.WaitFor.JavaScript("window.doneLoading = true")

renderer.RenderingOptions.RenderDelay = 200 ' ms
' OR: renderer.RenderingOptions.WaitFor.JavaScript("window.doneLoading = true")

See the dedicated WaitFor tutorial for custom promises and DOM polling.

4. Enable debug logging for one request

IronPdf.License.LicenseKey = "YourLicenseKey";
PdfDocument pdf = PdfDocument.FromFile("1.pdf");
PdfDocument pdf2 = PdfDocument.FromFile("2.pdf");
pdf.AppendPdf(pdf2);
pdf.SaveAs("appendedFile.pdf");

IronPdf.License.LicenseKey = "YourLicenseKey";
PdfDocument pdf = PdfDocument.FromFile("1.pdf");
PdfDocument pdf2 = PdfDocument.FromFile("2.pdf");
pdf.AppendPdf(pdf2);
pdf.SaveAs("appendedFile.pdf");

IronPdf.License.LicenseKey = "YourLicenseKey"
Dim pdf As PdfDocument = PdfDocument.FromFile("1.pdf")
Dim pdf2 As PdfDocument = PdfDocument.FromFile("2.pdf")
pdf.AppendPdf(pdf2)
pdf.SaveAs("appendedFile.pdf")

IronPdf.License.LicenseKey = "YourLicenseKey"
Dim pdf As PdfDocument = PdfDocument.FromFile("1.pdf")
Dim pdf2 As PdfDocument = PdfDocument.FromFile("2.pdf")
pdf.AppendPdf(pdf2)
pdf.SaveAs("appendedFile.pdf")

Live DevTools traces expose missing fonts, 404 images, and timing events without re-compiling code.

5. Reuse template PDFs instead of re-rendering

For invoice runs, create a template PDF with placeholders like [[name]] and perform a text replace instead of rebuilding complex HTML. It avoids re-rendering complex HTML and is memory-light.

Quick-Tuning Checklist

Further Reading

• How-to - Generate PDFs with async / multithreading
• Troubleshooting - Performance assistance centre
• Example - Threaded rendering demo

Where can I download a free trial, choose a license, and find expert support?

A 30-day trial key is issued instantly from the Start Free Trial form and unlocks every feature (including HTML-to-PDF, digital signatures, and encryption) without watermarking.

After evaluating the library, pick a perpetual developer, deployment, or enterprise license; each plan includes free minor updates, dev/staging/production usage rights, and a 30-day money-back guarantee. Applying the key is a single line of code (IronPdf.License.LicenseKey = "YOUR-KEY";) and can be automated in CI/CD pipelines.

Comprehensive documentation, quick-start guides, API reference, and tutorial videos, lives at the docs portal and is updated for every .NET release.

Engineering questions receive one-business-day responses via live chat, email, or phone from the Chicago-based support team.

Performance tuning and deployment FAQs are aggregated in the Performance Assistance Centre.

Quick links

Next steps

1. Clone the sample repo that demonstrates every major feature, from MVC view rendering to password-based encryption.
2. Plug the trial key into an existing solution and run the unit tests to validate cross-platform compatibility.
3. Book a live demo with the engineering team for project-specific recommendations.

With these resources in hand, any .NET team can ship pixel-perfect PDFs to production (on-prem, in Docker, or serverless) within a single sprint.

Jacob Mellor

Chief Technology Officer

Chat with engineering team now

Jacob Mellor is Chief Technology Officer at Iron Software and a visionary engineer pioneering C# PDF technology. As the original developer behind Iron Software's core codebase, he has shaped the company's product architecture since its inception, transforming it alongside CEO Cameron Rimington into a 50+ person company serving NASA, Tesla, and global government agencies.

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