The C# PDF Library

HTML to PDF

using IronPdf;

// Disable local disk access or cross-origin requests
Installation.EnableWebSecurity = true;

// Instantiate Renderer
var renderer = new ChromePdfRenderer();

// Create a PDF from a HTML string using C#
var pdf = renderer.RenderHtmlAsPdf("<h1>Hello World</h1>");

// Export to a file or Stream
pdf.SaveAs("output.pdf");

// Advanced Example with HTML Assets
// Load external html assets: Images, CSS and JavaScript.
// An optional BasePath 'C:\site\assets\' is set as the file location to load assets from
var myAdvancedPdf = renderer.RenderHtmlAsPdf("<img src='icons/iron.png'>", @"C:\site\assets\");
myAdvancedPdf.SaveAs("html-with-assets.pdf");

using IronPdf;

// Disable local disk access or cross-origin requests
Installation.EnableWebSecurity = true;

// Instantiate Renderer
var renderer = new ChromePdfRenderer();

// Create a PDF from a HTML string using C#
var pdf = renderer.RenderHtmlAsPdf("<h1>Hello World</h1>");

// Export to a file or Stream
pdf.SaveAs("output.pdf");

// Advanced Example with HTML Assets
// Load external html assets: Images, CSS and JavaScript.
// An optional BasePath 'C:\site\assets\' is set as the file location to load assets from
var myAdvancedPdf = renderer.RenderHtmlAsPdf("<img src='icons/iron.png'>", @"C:\site\assets\");
myAdvancedPdf.SaveAs("html-with-assets.pdf");

PM >Install-Package IronPdf

Install-Package IronPdf

MIGRATION GUIDES

How to Migrate from NReco PDF Generator to IronPDF in C#

Curtis Chau

Updated: July 19, 2026

Why Migrate from NReco PDF Generator to IronPDF

Critical Security Issues with NReco PDF Generator

NReco PDF Generator wraps the wkhtmltopdf binary, inheriting its known security vulnerabilities. The wkhtmltopdf project's last stable release was 0.12.6 (June 2020) and the upstream repository was archived on January 2, 2023, so no patches are coming:

CVE-2020-21365: Directory traversal / local file read via crafted HTML (same-origin policy weakness)
CVE-2022-35583: Server-side request forgery (SSRF) via injected <iframe> in 0.12.6 (CVSS 9.8)

Additional NReco PDF Generator Limitations

Licensing friction at scale: Free for non-SaaS single-server production deployments; SaaS, multi-server, or redistribution scenarios require the $199 enterprise source-code pack from nrecosite.com.
Deprecated Rendering Engine: WebKit Qt (circa 2012) with limited CSS3/JS support:
- No CSS Grid or Flexbox
- No modern JavaScript (ES6+)
- Poor web font support
- No CSS variables or custom properties
External Binary Dependency: Requires managing wkhtmltopdf binaries per platform (wkhtmltopdf.exe, wkhtmltox.dll).
Stalled maintenance: NReco.PdfGenerator 1.2.1 was published Jan 8, 2023 and has had no further releases on nuget.org; the underlying wkhtmltopdf engine is no longer updated.
Limited Async Support: Synchronous API blocks threads in web applications.

NReco PDF Generator vs IronPDF Comparison

Aspect	NReco PDF Generator	IronPDF
Rendering Engine	WebKit Qt (2012)	Chromium (current)
Security	Multiple unpatched CVEs (e.g., CVE-2020-21365, CVE-2022-35583); engine archived Jan 2, 2023	Active security updates
CSS Support	CSS2.1, limited CSS3	Full CSS3, Grid, Flexbox
JavaScript	Basic ES5	Full ES6+, async/await
Dependencies	External wkhtmltopdf binary	Self-contained
Async Support	Synchronous only	Full async/await
Web Fonts	Limited	Full Google Fonts, @font-face
Licensing	Free for non-SaaS single-server; $199 enterprise pack for SaaS / multi-server	Transparent commercial pricing
Free Tier	Free under non-SaaS single-server license	Trial requires no watermark

Before You Start

Prerequisites

.NET Environment: .NET Framework 4.6.2+ or .NET Core 3.1+ / .NET 5/6/7/8/9+
NuGet Access: Ability to install NuGet packages
IronPDF License: Obtain your license key from ironpdf.com

NuGet Package Changes

# Remove NReco.PdfGenerator
dotnet remove package NReco.PdfGenerator

# Install IronPDF
dotnet add package IronPdf

# Remove NReco.PdfGenerator
dotnet remove package NReco.PdfGenerator

# Install IronPDF
dotnet add package IronPdf

SHELL

Also remove wkhtmltopdf binaries from your deployment:

Delete wkhtmltopdf.exe, wkhtmltox.dll from project
Remove any wkhtmltopdf installation scripts
Delete platform-specific binary folders

License Configuration

// Add at application startup (Program.cs or Startup.cs)
IronPdf.License.LicenseKey = "YOUR-LICENSE-KEY";

// Add at application startup (Program.cs or Startup.cs)
IronPdf.License.LicenseKey = "YOUR-LICENSE-KEY";

' Add at application startup (Program.vb or Startup.vb)
IronPdf.License.LicenseKey = "YOUR-LICENSE-KEY"

' Add at application startup (Program.vb or Startup.vb)
IronPdf.License.LicenseKey = "YOUR-LICENSE-KEY"

Identify NReco PDF Generator Usage

# Find all NReco.PdfGenerator references
grep -r "NReco.PdfGenerator\|HtmlToPdfConverter\|GeneratePdf" --include="*.cs" .

# Find all NReco.PdfGenerator references
grep -r "NReco.PdfGenerator\|HtmlToPdfConverter\|GeneratePdf" --include="*.cs" .

SHELL

Complete API Reference

Core Class Mappings

NReco PDF Generator	IronPDF
`HtmlToPdfConverter`	`ChromePdfRenderer`
`PageMargins`	Individual margin properties
`PageOrientation`	`PdfPaperOrientation`
`PageSize`	`PdfPaperSize`

Rendering Method Mappings

NReco PDF Generator	IronPDF
`GeneratePdf(html)`	`RenderHtmlAsPdf(html)`
`GeneratePdfFromFile(url, output)`	`RenderUrlAsPdf(url)`
`GeneratePdfFromFile(htmlPath, output)`	`RenderHtmlFileAsPdf(path)`
(async not supported)	`RenderHtmlAsPdfAsync(html)`
(async not supported)	`RenderUrlAsPdfAsync(url)`

Page Configuration Mappings

NReco PDF Generator	IronPDF
`PageWidth = 210`	`RenderingOptions.PaperSize = PdfPaperSize.A4`
`PageHeight = 297`	`RenderingOptions.SetCustomPaperSizeinMilimeters(w, h)`
`Orientation = PageOrientation.Landscape`	`RenderingOptions.PaperOrientation = PdfPaperOrientation.Landscape`
`Size = PageSize.A4`	`RenderingOptions.PaperSize = PdfPaperSize.A4`

Margin Mappings

NReco PDF Generator	IronPDF
`Margins.Top = 10`	`RenderingOptions.MarginTop = 10`
`Margins.Bottom = 10`	`RenderingOptions.MarginBottom = 10`
`Margins.Left = 10`	`RenderingOptions.MarginLeft = 10`
`Margins.Right = 10`	`RenderingOptions.MarginRight = 10`
`new PageMargins { ... }`	Individual properties

Header/Footer Placeholder Mappings

NReco PDF Generator (wkhtmltopdf)	IronPDF
`[page]`	`{page}`
`[topage]`	`{total-pages}`
`[date]`	`{date}`
`[time]`	`{time}`
`[title]`	`{html-title}`

Output Handling Mappings

NReco PDF Generator	IronPDF
`byte[] pdfBytes = GeneratePdf(html)`	`PdfDocument pdf = RenderHtmlAsPdf(html)`
`File.WriteAllBytes(path, bytes)`	`pdf.SaveAs(path)`
`return pdfBytes`	`return pdf.BinaryData`
`new MemoryStream(pdfBytes)`	`new MemoryStream(pdf.BinaryData)`

Code Migration Examples

Example 1: Basic HTML to PDF

Before (NReco PDF Generator):

// NuGet: Install-Package NReco.PdfGenerator
using NReco.PdfGenerator;
using System.IO;

class Program
{
    static void Main()
    {
        var htmlToPdf = new HtmlToPdfConverter();
        var htmlContent = "<html><body><h1>Hello World</h1><p>This is a PDF document.</p></body></html>";
        var pdfBytes = htmlToPdf.GeneratePdf(htmlContent);
        File.WriteAllBytes("output.pdf", pdfBytes);
    }
}

// NuGet: Install-Package NReco.PdfGenerator
using NReco.PdfGenerator;
using System.IO;

class Program
{
    static void Main()
    {
        var htmlToPdf = new HtmlToPdfConverter();
        var htmlContent = "<html><body><h1>Hello World</h1><p>This is a PDF document.</p></body></html>";
        var pdfBytes = htmlToPdf.GeneratePdf(htmlContent);
        File.WriteAllBytes("output.pdf", pdfBytes);
    }
}

Imports NReco.PdfGenerator
Imports System.IO

Class Program
    Shared Sub Main()
        Dim htmlToPdf = New HtmlToPdfConverter()
        Dim htmlContent = "<html><body><h1>Hello World</h1><p>This is a PDF document.</p></body></html>"
        Dim pdfBytes = htmlToPdf.GeneratePdf(htmlContent)
        File.WriteAllBytes("output.pdf", pdfBytes)
    End Sub
End Class

Imports NReco.PdfGenerator
Imports System.IO

Class Program
    Shared Sub Main()
        Dim htmlToPdf = New HtmlToPdfConverter()
        Dim htmlContent = "<html><body><h1>Hello World</h1><p>This is a PDF document.</p></body></html>"
        Dim pdfBytes = htmlToPdf.GeneratePdf(htmlContent)
        File.WriteAllBytes("output.pdf", pdfBytes)
    End Sub
End Class

After (IronPDF):

// NuGet: Install-Package IronPdf
using IronPdf;
using System.IO;

class Program
{
    static void Main()
    {
        var renderer = new ChromePdfRenderer();
        var htmlContent = "<html><body><h1>Hello World</h1><p>This is a PDF document.</p></body></html>";
        var pdf = renderer.RenderHtmlAsPdf(htmlContent);
        pdf.SaveAs("output.pdf");
    }
}

// NuGet: Install-Package IronPdf
using IronPdf;
using System.IO;

class Program
{
    static void Main()
    {
        var renderer = new ChromePdfRenderer();
        var htmlContent = "<html><body><h1>Hello World</h1><p>This is a PDF document.</p></body></html>";
        var pdf = renderer.RenderHtmlAsPdf(htmlContent);
        pdf.SaveAs("output.pdf");
    }
}

Imports IronPdf
Imports System.IO

Class Program
    Shared Sub Main()
        Dim renderer = New ChromePdfRenderer()
        Dim htmlContent = "<html><body><h1>Hello World</h1><p>This is a PDF document.</p></body></html>"
        Dim pdf = renderer.RenderHtmlAsPdf(htmlContent)
        pdf.SaveAs("output.pdf")
    End Sub
End Class

Imports IronPdf
Imports System.IO

Class Program
    Shared Sub Main()
        Dim renderer = New ChromePdfRenderer()
        Dim htmlContent = "<html><body><h1>Hello World</h1><p>This is a PDF document.</p></body></html>"
        Dim pdf = renderer.RenderHtmlAsPdf(htmlContent)
        pdf.SaveAs("output.pdf")
    End Sub
End Class

The fundamental difference is in the return type and save pattern. NReco PDF Generator's HtmlToPdfConverter.GeneratePdf() returns a byte[] that you must manually write to disk using File.WriteAllBytes(). IronPDF's ChromePdfRenderer.RenderHtmlAsPdf() returns a PdfDocument object with a built-in SaveAs() method.

This object-oriented approach provides additional benefits: you can manipulate the PDF (add watermarks, merge documents, add security) before saving. If you need the raw bytes for compatibility with existing code, use pdf.BinaryData. See the HTML to PDF documentation for additional rendering options.

Example 2: Custom Page Size with Margins

Before (NReco PDF Generator):

// NuGet: Install-Package NReco.PdfGenerator
using NReco.PdfGenerator;
using System.IO;

class Program
{
    static void Main()
    {
        var htmlToPdf = new HtmlToPdfConverter();
        htmlToPdf.PageWidth = 210;
        htmlToPdf.PageHeight = 297;
        htmlToPdf.Margins = new PageMargins { Top = 10, Bottom = 10, Left = 10, Right = 10 };
        var htmlContent = "<html><body><h1>Custom Page Size</h1><p>A4 size document with margins.</p></body></html>";
        var pdfBytes = htmlToPdf.GeneratePdf(htmlContent);
        File.WriteAllBytes("custom-size.pdf", pdfBytes);
    }
}

// NuGet: Install-Package NReco.PdfGenerator
using NReco.PdfGenerator;
using System.IO;

class Program
{
    static void Main()
    {
        var htmlToPdf = new HtmlToPdfConverter();
        htmlToPdf.PageWidth = 210;
        htmlToPdf.PageHeight = 297;
        htmlToPdf.Margins = new PageMargins { Top = 10, Bottom = 10, Left = 10, Right = 10 };
        var htmlContent = "<html><body><h1>Custom Page Size</h1><p>A4 size document with margins.</p></body></html>";
        var pdfBytes = htmlToPdf.GeneratePdf(htmlContent);
        File.WriteAllBytes("custom-size.pdf", pdfBytes);
    }
}

Imports NReco.PdfGenerator
Imports System.IO

Class Program
    Shared Sub Main()
        Dim htmlToPdf = New HtmlToPdfConverter()
        htmlToPdf.PageWidth = 210
        htmlToPdf.PageHeight = 297
        htmlToPdf.Margins = New PageMargins With {.Top = 10, .Bottom = 10, .Left = 10, .Right = 10}
        Dim htmlContent = "<html><body><h1>Custom Page Size</h1><p>A4 size document with margins.</p></body></html>"
        Dim pdfBytes = htmlToPdf.GeneratePdf(htmlContent)
        File.WriteAllBytes("custom-size.pdf", pdfBytes)
    End Sub
End Class

Imports NReco.PdfGenerator
Imports System.IO

Class Program
    Shared Sub Main()
        Dim htmlToPdf = New HtmlToPdfConverter()
        htmlToPdf.PageWidth = 210
        htmlToPdf.PageHeight = 297
        htmlToPdf.Margins = New PageMargins With {.Top = 10, .Bottom = 10, .Left = 10, .Right = 10}
        Dim htmlContent = "<html><body><h1>Custom Page Size</h1><p>A4 size document with margins.</p></body></html>"
        Dim pdfBytes = htmlToPdf.GeneratePdf(htmlContent)
        File.WriteAllBytes("custom-size.pdf", pdfBytes)
    End Sub
End Class

After (IronPDF):

// NuGet: Install-Package IronPdf
using IronPdf;
using IronPdf.Rendering;

class Program
{
    static void Main()
    {
        var renderer = new ChromePdfRenderer();
        renderer.RenderingOptions.PaperSize = PdfPaperSize.A4;
        renderer.RenderingOptions.MarginTop = 10;
        renderer.RenderingOptions.MarginBottom = 10;
        renderer.RenderingOptions.MarginLeft = 10;
        renderer.RenderingOptions.MarginRight = 10;
        var htmlContent = "<html><body><h1>Custom Page Size</h1><p>A4 size document with margins.</p></body></html>";
        var pdf = renderer.RenderHtmlAsPdf(htmlContent);
        pdf.SaveAs("custom-size.pdf");
    }
}

// NuGet: Install-Package IronPdf
using IronPdf;
using IronPdf.Rendering;

class Program
{
    static void Main()
    {
        var renderer = new ChromePdfRenderer();
        renderer.RenderingOptions.PaperSize = PdfPaperSize.A4;
        renderer.RenderingOptions.MarginTop = 10;
        renderer.RenderingOptions.MarginBottom = 10;
        renderer.RenderingOptions.MarginLeft = 10;
        renderer.RenderingOptions.MarginRight = 10;
        var htmlContent = "<html><body><h1>Custom Page Size</h1><p>A4 size document with margins.</p></body></html>";
        var pdf = renderer.RenderHtmlAsPdf(htmlContent);
        pdf.SaveAs("custom-size.pdf");
    }
}

Imports IronPdf
Imports IronPdf.Rendering

Class Program
    Shared Sub Main()
        Dim renderer = New ChromePdfRenderer()
        renderer.RenderingOptions.PaperSize = PdfPaperSize.A4
        renderer.RenderingOptions.MarginTop = 10
        renderer.RenderingOptions.MarginBottom = 10
        renderer.RenderingOptions.MarginLeft = 10
        renderer.RenderingOptions.MarginRight = 10
        Dim htmlContent = "<html><body><h1>Custom Page Size</h1><p>A4 size document with margins.</p></body></html>"
        Dim pdf = renderer.RenderHtmlAsPdf(htmlContent)
        pdf.SaveAs("custom-size.pdf")
    End Sub
End Class

Imports IronPdf
Imports IronPdf.Rendering

Class Program
    Shared Sub Main()
        Dim renderer = New ChromePdfRenderer()
        renderer.RenderingOptions.PaperSize = PdfPaperSize.A4
        renderer.RenderingOptions.MarginTop = 10
        renderer.RenderingOptions.MarginBottom = 10
        renderer.RenderingOptions.MarginLeft = 10
        renderer.RenderingOptions.MarginRight = 10
        Dim htmlContent = "<html><body><h1>Custom Page Size</h1><p>A4 size document with margins.</p></body></html>"
        Dim pdf = renderer.RenderHtmlAsPdf(htmlContent)
        pdf.SaveAs("custom-size.pdf")
    End Sub
End Class

NReco PDF Generator uses numeric dimensions (PageWidth = 210, PageHeight = 297) and a PageMargins object. IronPDF uses the PdfPaperSize enum (which includes standard sizes like A4, Letter, Legal) and individual margin properties on the RenderingOptions object.

The key migration changes:

PageWidth/PageHeight → RenderingOptions.PaperSize = PdfPaperSize.A4
new PageMargins { Top = 10, ... } → Individual properties: RenderingOptions.MarginTop = 10

For custom paper sizes not covered by the enum, use RenderingOptions.SetCustomPaperSizeinMilimeters(width, height). Learn more about page configuration options.

Example 3: URL to PDF Conversion

Before (NReco PDF Generator):

// NuGet: Install-Package NReco.PdfGenerator
using NReco.PdfGenerator;
using System.IO;

class Program
{
    static void Main()
    {
        var htmlToPdf = new HtmlToPdfConverter();
        var pdfBytes = htmlToPdf.GeneratePdfFromFile("https://www.example.com", null);
        File.WriteAllBytes("webpage.pdf", pdfBytes);
    }
}

// NuGet: Install-Package NReco.PdfGenerator
using NReco.PdfGenerator;
using System.IO;

class Program
{
    static void Main()
    {
        var htmlToPdf = new HtmlToPdfConverter();
        var pdfBytes = htmlToPdf.GeneratePdfFromFile("https://www.example.com", null);
        File.WriteAllBytes("webpage.pdf", pdfBytes);
    }
}

Imports NReco.PdfGenerator
Imports System.IO

Class Program
    Shared Sub Main()
        Dim htmlToPdf As New HtmlToPdfConverter()
        Dim pdfBytes As Byte() = htmlToPdf.GeneratePdfFromFile("https://www.example.com", Nothing)
        File.WriteAllBytes("webpage.pdf", pdfBytes)
    End Sub
End Class

Imports NReco.PdfGenerator
Imports System.IO

Class Program
    Shared Sub Main()
        Dim htmlToPdf As New HtmlToPdfConverter()
        Dim pdfBytes As Byte() = htmlToPdf.GeneratePdfFromFile("https://www.example.com", Nothing)
        File.WriteAllBytes("webpage.pdf", pdfBytes)
    End Sub
End Class

After (IronPDF):

// NuGet: Install-Package IronPdf
using IronPdf;

class Program
{
    static void Main()
    {
        var renderer = new ChromePdfRenderer();
        var pdf = renderer.RenderUrlAsPdf("https://www.example.com");
        pdf.SaveAs("webpage.pdf");
    }
}

// NuGet: Install-Package IronPdf
using IronPdf;

class Program
{
    static void Main()
    {
        var renderer = new ChromePdfRenderer();
        var pdf = renderer.RenderUrlAsPdf("https://www.example.com");
        pdf.SaveAs("webpage.pdf");
    }
}

Imports IronPdf

Class Program
    Shared Sub Main()
        Dim renderer As New ChromePdfRenderer()
        Dim pdf = renderer.RenderUrlAsPdf("https://www.example.com")
        pdf.SaveAs("webpage.pdf")
    End Sub
End Class

Imports IronPdf

Class Program
    Shared Sub Main()
        Dim renderer As New ChromePdfRenderer()
        Dim pdf = renderer.RenderUrlAsPdf("https://www.example.com")
        pdf.SaveAs("webpage.pdf")
    End Sub
End Class

NReco PDF Generator uses the confusingly named GeneratePdfFromFile() method for both local files and URLs, with a nullable second parameter. IronPDF provides dedicated methods: RenderUrlAsPdf() for URLs and RenderHtmlFileAsPdf() for local HTML files.

The IronPDF approach is cleaner and more intuitive. For async web applications, use await renderer.RenderUrlAsPdfAsync(url) to avoid blocking threads - something NReco PDF Generator simply cannot do.

Critical Migration Notes

Zoom Value Conversion

NReco PDF Generator uses float values (0.0-2.0), while IronPDF uses percentage integers:

// NReco PDF Generator: Zoom = 0.9f (90%)
// IronPDF: Zoom = 90

// Conversion formula:
int ironPdfZoom = (int)(nrecoZoom * 100);

// NReco PDF Generator: Zoom = 0.9f (90%)
// IronPDF: Zoom = 90

// Conversion formula:
int ironPdfZoom = (int)(nrecoZoom * 100);

' NReco PDF Generator: Zoom = 0.9F (90%)
' IronPDF: Zoom = 90

' Conversion formula:
Dim ironPdfZoom As Integer = CInt(nrecoZoom * 100)

' NReco PDF Generator: Zoom = 0.9F (90%)
' IronPDF: Zoom = 90

' Conversion formula:
Dim ironPdfZoom As Integer = CInt(nrecoZoom * 100)

Placeholder Syntax Update

All header/footer placeholders must be updated:

NReco PDF Generator	IronPDF
`[page]`	`{page}`
`[topage]`	`{total-pages}`
`[date]`	`{date}`
`[title]`	`{html-title}`

// NReco PDF Generator:
converter.PageFooterHtml = "<div>Page [page] of [topage]</div>";

// IronPDF:
renderer.RenderingOptions.HtmlFooter = new HtmlHeaderFooter
{
    HtmlFragment = "<div>Page {page} of {total-pages}</div>",
    MaxHeight = 20
};

// NReco PDF Generator:
converter.PageFooterHtml = "<div>Page [page] of [topage]</div>";

// IronPDF:
renderer.RenderingOptions.HtmlFooter = new HtmlHeaderFooter
{
    HtmlFragment = "<div>Page {page} of {total-pages}</div>",
    MaxHeight = 20
};

Imports NReco.PdfGenerator
Imports IronPdf

' NReco PDF Generator:
converter.PageFooterHtml = "<div>Page [page] of [topage]</div>"

' IronPDF:
renderer.RenderingOptions.HtmlFooter = New HtmlHeaderFooter With {
    .HtmlFragment = "<div>Page {page} of {total-pages}</div>",
    .MaxHeight = 20
}

Imports NReco.PdfGenerator
Imports IronPdf

' NReco PDF Generator:
converter.PageFooterHtml = "<div>Page [page] of [topage]</div>"

' IronPDF:
renderer.RenderingOptions.HtmlFooter = New HtmlHeaderFooter With {
    .HtmlFragment = "<div>Page {page} of {total-pages}</div>",
    .MaxHeight = 20
}

Return Type Change

NReco PDF Generator returns byte[] directly; IronPDF returns PdfDocument:

// NReco PDF Generator pattern:
byte[] pdfBytes = converter.GeneratePdf(html);
File.WriteAllBytes("output.pdf", pdfBytes);

// IronPDF pattern:
var pdf = renderer.RenderHtmlAsPdf(html);
pdf.SaveAs("output.pdf");

// Or if you need bytes:
byte[] pdfBytes = renderer.RenderHtmlAsPdf(html).BinaryData;

// NReco PDF Generator pattern:
byte[] pdfBytes = converter.GeneratePdf(html);
File.WriteAllBytes("output.pdf", pdfBytes);

// IronPDF pattern:
var pdf = renderer.RenderHtmlAsPdf(html);
pdf.SaveAs("output.pdf");

// Or if you need bytes:
byte[] pdfBytes = renderer.RenderHtmlAsPdf(html).BinaryData;

' NReco PDF Generator pattern:
Dim pdfBytes As Byte() = converter.GeneratePdf(html)
File.WriteAllBytes("output.pdf", pdfBytes)

' IronPDF pattern:
Dim pdf = renderer.RenderHtmlAsPdf(html)
pdf.SaveAs("output.pdf")

' Or if you need bytes:
Dim pdfBytes As Byte() = renderer.RenderHtmlAsPdf(html).BinaryData

' NReco PDF Generator pattern:
Dim pdfBytes As Byte() = converter.GeneratePdf(html)
File.WriteAllBytes("output.pdf", pdfBytes)

' IronPDF pattern:
Dim pdf = renderer.RenderHtmlAsPdf(html)
pdf.SaveAs("output.pdf")

' Or if you need bytes:
Dim pdfBytes As Byte() = renderer.RenderHtmlAsPdf(html).BinaryData

Thread Safety and Reusability

NReco PDF Generator typically creates a new converter per call. IronPDF's ChromePdfRenderer is thread-safe and can be reused:

// NReco PDF Generator pattern (creates new each time):
public byte[] Generate(string html)
{
    var converter = new HtmlToPdfConverter();
    return converter.GeneratePdf(html);
}

// IronPDF pattern (reuse renderer, thread-safe):
private readonly ChromePdfRenderer _renderer = new ChromePdfRenderer();

public byte[] Generate(string html)
{
    return _renderer.RenderHtmlAsPdf(html).BinaryData;
}

// NReco PDF Generator pattern (creates new each time):
public byte[] Generate(string html)
{
    var converter = new HtmlToPdfConverter();
    return converter.GeneratePdf(html);
}

// IronPDF pattern (reuse renderer, thread-safe):
private readonly ChromePdfRenderer _renderer = new ChromePdfRenderer();

public byte[] Generate(string html)
{
    return _renderer.RenderHtmlAsPdf(html).BinaryData;
}

' NReco PDF Generator pattern (creates new each time):
Public Function Generate(html As String) As Byte()
    Dim converter As New HtmlToPdfConverter()
    Return converter.GeneratePdf(html)
End Function

' IronPDF pattern (reuse renderer, thread-safe):
Private ReadOnly _renderer As New ChromePdfRenderer()

Public Function Generate(html As String) As Byte()
    Return _renderer.RenderHtmlAsPdf(html).BinaryData
End Function

' NReco PDF Generator pattern (creates new each time):
Public Function Generate(html As String) As Byte()
    Dim converter As New HtmlToPdfConverter()
    Return converter.GeneratePdf(html)
End Function

' IronPDF pattern (reuse renderer, thread-safe):
Private ReadOnly _renderer As New ChromePdfRenderer()

Public Function Generate(html As String) As Byte()
    Return _renderer.RenderHtmlAsPdf(html).BinaryData
End Function

Async Support (New Capability)

IronPDF supports async/await patterns that NReco PDF Generator cannot provide:

// NReco PDF Generator: No async support available

// IronPDF: Full async support
public async Task<byte[]> GenerateAsync(string html)
{
    var pdf = await _renderer.RenderHtmlAsPdfAsync(html);
    return pdf.BinaryData;
}

// NReco PDF Generator: No async support available

// IronPDF: Full async support
public async Task<byte[]> GenerateAsync(string html)
{
    var pdf = await _renderer.RenderHtmlAsPdfAsync(html);
    return pdf.BinaryData;
}

Imports System.Threading.Tasks

' NReco PDF Generator: No async support available

' IronPDF: Full async support
Public Async Function GenerateAsync(html As String) As Task(Of Byte())
    Dim pdf = Await _renderer.RenderHtmlAsPdfAsync(html)
    Return pdf.BinaryData
End Function

Imports System.Threading.Tasks

' NReco PDF Generator: No async support available

' IronPDF: Full async support
Public Async Function GenerateAsync(html As String) As Task(Of Byte())
    Dim pdf = Await _renderer.RenderHtmlAsPdfAsync(html)
    Return pdf.BinaryData
End Function

Troubleshooting

Issue 1: HtmlToPdfConverter Not Found

Problem: HtmlToPdfConverter class doesn't exist in IronPDF.

Solution: Use ChromePdfRenderer:

// NReco PDF Generator
var converter = new HtmlToPdfConverter();

// IronPDF
var renderer = new ChromePdfRenderer();

// NReco PDF Generator
var converter = new HtmlToPdfConverter();

// IronPDF
var renderer = new ChromePdfRenderer();

' NReco PDF Generator
Dim converter As New HtmlToPdfConverter()

' IronPDF
Dim renderer As New ChromePdfRenderer()

' NReco PDF Generator
Dim converter As New HtmlToPdfConverter()

' IronPDF
Dim renderer As New ChromePdfRenderer()

Issue 2: GeneratePdf Returns Wrong Type

Problem: Code expects byte[] but gets PdfDocument.

Solution: Access .BinaryData property:

// NReco PDF Generator
byte[] pdfBytes = converter.GeneratePdf(html);

// IronPDF
byte[] pdfBytes = renderer.RenderHtmlAsPdf(html).BinaryData;

// NReco PDF Generator
byte[] pdfBytes = converter.GeneratePdf(html);

// IronPDF
byte[] pdfBytes = renderer.RenderHtmlAsPdf(html).BinaryData;

' NReco PDF Generator
Dim pdfBytes As Byte() = converter.GeneratePdf(html)

' IronPDF
Dim pdfBytes As Byte() = renderer.RenderHtmlAsPdf(html).BinaryData

' NReco PDF Generator
Dim pdfBytes As Byte() = converter.GeneratePdf(html)

' IronPDF
Dim pdfBytes As Byte() = renderer.RenderHtmlAsPdf(html).BinaryData

Issue 3: PageMargins Object Not Found

Problem: PageMargins class doesn't exist in IronPDF.

Solution: Use individual margin properties:

// NReco PDF Generator
converter.Margins = new PageMargins { Top = 10, Bottom = 10, Left = 10, Right = 10 };

// IronPDF
renderer.RenderingOptions.MarginTop = 10;
renderer.RenderingOptions.MarginBottom = 10;
renderer.RenderingOptions.MarginLeft = 10;
renderer.RenderingOptions.MarginRight = 10;

// NReco PDF Generator
converter.Margins = new PageMargins { Top = 10, Bottom = 10, Left = 10, Right = 10 };

// IronPDF
renderer.RenderingOptions.MarginTop = 10;
renderer.RenderingOptions.MarginBottom = 10;
renderer.RenderingOptions.MarginLeft = 10;
renderer.RenderingOptions.MarginRight = 10;

' NReco PDF Generator
converter.Margins = New PageMargins With {.Top = 10, .Bottom = 10, .Left = 10, .Right = 10}

' IronPDF
renderer.RenderingOptions.MarginTop = 10
renderer.RenderingOptions.MarginBottom = 10
renderer.RenderingOptions.MarginLeft = 10
renderer.RenderingOptions.MarginRight = 10

' NReco PDF Generator
converter.Margins = New PageMargins With {.Top = 10, .Bottom = 10, .Left = 10, .Right = 10}

' IronPDF
renderer.RenderingOptions.MarginTop = 10
renderer.RenderingOptions.MarginBottom = 10
renderer.RenderingOptions.MarginLeft = 10
renderer.RenderingOptions.MarginRight = 10

Issue 4: Page Numbers Not Appearing

Problem: [page] and [topage] placeholders don't work.

Solution: Update to IronPDF placeholder syntax:

// NReco PDF Generator
converter.PageFooterHtml = "<div>Page [page] of [topage]</div>";

// IronPDF
renderer.RenderingOptions.HtmlFooter = new HtmlHeaderFooter
{
    HtmlFragment = "<div>Page {page} of {total-pages}</div>",
    MaxHeight = 20
};

// NReco PDF Generator
converter.PageFooterHtml = "<div>Page [page] of [topage]</div>";

// IronPDF
renderer.RenderingOptions.HtmlFooter = new HtmlHeaderFooter
{
    HtmlFragment = "<div>Page {page} of {total-pages}</div>",
    MaxHeight = 20
};

Imports NReco.PdfGenerator
Imports IronPdf

converter.PageFooterHtml = "<div>Page [page] of [topage]</div>"

renderer.RenderingOptions.HtmlFooter = New HtmlHeaderFooter With {
    .HtmlFragment = "<div>Page {page} of {total-pages}</div>",
    .MaxHeight = 20
}

Imports NReco.PdfGenerator
Imports IronPdf

converter.PageFooterHtml = "<div>Page [page] of [topage]</div>"

renderer.RenderingOptions.HtmlFooter = New HtmlHeaderFooter With {
    .HtmlFragment = "<div>Page {page} of {total-pages}</div>",
    .MaxHeight = 20
}

Migration Checklist

Pre-Migration

Inventory all NReco.PdfGenerator usages in codebase
Document all CustomWkHtmlArgs and CustomWkHtmlPageArgs values
List all header/footer HTML templates with placeholders
Identify async requirements (web controllers, services)
Review zoom and margin settings
Backup existing PDF outputs for comparison
Obtain IronPDF license key

Package Changes

Remove NReco.PdfGenerator NuGet package
Install IronPdf NuGet package: dotnet add package IronPdf
Update namespace imports from using NReco.PdfGenerator; to using IronPdf;

Code Changes

Add license key configuration at startup
Replace HtmlToPdfConverter with ChromePdfRenderer
Replace GeneratePdf(html) with RenderHtmlAsPdf(html)
Replace GeneratePdfFromFile(url, null) with RenderUrlAsPdf(url)
Convert PageMargins object to individual margin properties
Update zoom values from float to percentage
Update placeholder syntax: [page] → {page}, [topage] → {total-pages}
Replace File.WriteAllBytes() with pdf.SaveAs()
Convert sync calls to async where beneficial

Post-Migration

Remove wkhtmltopdf binaries from project/deployment
Update Docker files to remove wkhtmltopdf installation
Run regression tests comparing PDF output
Verify header/footer placeholders render correctly
Test on all target platforms (Windows, Linux, macOS)
Update CI/CD pipeline to remove wkhtmltopdf steps
Update security scanning to confirm CVE removal

Please note: NReco and wkhtmltopdf are registered trademarks of their respective owners. This site is not affiliated with, endorsed by, or sponsored by NReco or wkhtmltopdf. All product names, logos, and brands are property of their respective owners. Comparisons are for informational purposes only and reflect publicly available information at the time of writing.

Curtis Chau

Chat with engineering team now

Technical Writer

Curtis Chau holds a Bachelor’s degree in Computer Science (Carleton University) and specializes in front-end development with expertise in Node.js, TypeScript, JavaScript, and React. Passionate about crafting intuitive and aesthetically pleasing user interfaces, Curtis enjoys working with modern frameworks and creating well-structured, visually appealing manuals.

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