Create PDF in ASP.NET: iTextSharp vs IronPDF

What Are the Key Differences Between iTextSharp and IronPDF?

iTextSharp is a .NET port of the Java iText library, offering programmatic PDF creation through its document class and low-level PDF content manipulation. While powerful, using iTextSharp requires understanding PDF document structure, working with document objects, and manually positioning elements using coordinates and page size specifications. The API is verbose by necessity -- the library exposes the full complexity of the PDF specification, which means there is a lot to learn before producing polished output.

IronPDF takes a different approach, focusing on HTML-to-PDF conversion using a Chrome rendering engine. Developers can generate PDF files using familiar HTML and CSS, making PDF creation as straightforward as designing a web page. IronPDF handles the PDF generation logic behind the scenes, allowing you to produce documents with modern styling and JavaScript support. Because the rendering pipeline is powered by Chromium, any layout that works in a modern browser will translate faithfully to the PDF output -- including flexbox, grid, web fonts, and JavaScript-generated content.

The practical consequence of this architectural difference is that iTextSharp rewards developers who want fine-grained, coordinate-level control over every byte in a PDF file, while IronPDF rewards developers who want to produce visually polished documents quickly using skills they already have. For most web application scenarios -- invoices, reports, order confirmations, and data exports -- the HTML approach is faster to build and easier to maintain.

How Do You Install These Libraries in a .NET Project?

Installing either library starts with the NuGet Package Manager. For iTextSharp, note that newer iText versions operate under the AGPL license, which requires either open-sourcing your application or purchasing a commercial license:

# Install iTextSharp via Package Manager Console
Install-Package iTextSharp

# Install iTextSharp via Package Manager Console
Install-Package iTextSharp

For IronPDF, you can install it through the NuGet Package Manager Console, the .NET CLI, or by searching directly in Visual Studio's NuGet UI:

Install-Package IronPdf

After installation, IronPDF is ready to use with a single using statement. No additional configuration is required for basic PDF generation. For advanced scenarios -- such as setting a license key, configuring rendering options, or generating PDFs in a cloud environment -- see the IronPDF documentation. IronPDF supports Linux, macOS, and Windows deployments, including containerized environments running in Docker or Kubernetes, which makes it well-suited for modern cloud-native ASP.NET applications.

How Do You Create a Basic PDF Document with Each Library?

The clearest way to understand the API difference is to create a simple "Hello World" PDF with both libraries side by side.

using iTextSharp.text;
using iTextSharp.text.pdf;

var memoryStream = new MemoryStream();
Document pdfDoc = new Document(PageSize.A4, 25, 25, 25, 15);
PdfWriter writer = PdfWriter.GetInstance(pdfDoc, memoryStream);
pdfDoc.Open();

var paragraph = new Paragraph("Hello World - PDF Document");
paragraph.Font = FontFactory.GetFont(FontFactory.HELVETICA, 16);
pdfDoc.Add(paragraph);
pdfDoc.Add(new Paragraph("Creating PDF documents with iTextSharp"));

pdfDoc.Close();

// Return as a downloadable file
var pdfBytes = memoryStream.ToArray();

using iTextSharp.text;
using iTextSharp.text.pdf;

var memoryStream = new MemoryStream();
Document pdfDoc = new Document(PageSize.A4, 25, 25, 25, 15);
PdfWriter writer = PdfWriter.GetInstance(pdfDoc, memoryStream);
pdfDoc.Open();

var paragraph = new Paragraph("Hello World - PDF Document");
paragraph.Font = FontFactory.GetFont(FontFactory.HELVETICA, 16);
pdfDoc.Add(paragraph);
pdfDoc.Add(new Paragraph("Creating PDF documents with iTextSharp"));

pdfDoc.Close();

// Return as a downloadable file
var pdfBytes = memoryStream.ToArray();

using IronPdf;

var renderer = new ChromePdfRenderer();
var pdf = renderer.RenderHtmlAsPdf(@"
    <h1>Hello World - PDF Document</h1>
    <p>Creating PDFs with IronPDF is straightforward!</p>
");

var pdfBytes = pdf.BinaryData;

using IronPdf;

var renderer = new ChromePdfRenderer();
var pdf = renderer.RenderHtmlAsPdf(@"
    <h1>Hello World - PDF Document</h1>
    <p>Creating PDFs with IronPDF is straightforward!</p>
");

var pdfBytes = pdf.BinaryData;

How Do You Create Styled PDFs with Images and CSS?

Styled documents reveal the most significant gap between the two libraries. When generating invoices, reports, or branded documents, CSS-based styling in IronPDF dramatically reduces the amount of code required.

using IronPdf;

var html = @"
    <style>
        body { font-family: Arial, sans-serif; margin: 0; }
        .invoice-header { background: #4CAF50; color: white; padding: 20px; }
        .invoice-table { width: 100%; border-collapse: collapse; margin-top: 20px; }
        .invoice-table th, .invoice-table td {
            border: 1px solid #ddd; padding: 8px; text-align: left;
        }
        .invoice-table th { background-color: #f2f2f2; }
        .total { font-size: 18px; font-weight: bold; margin-top: 16px; }
    </style>
    <div class='invoice-header'>
        <h1>Invoice #2024-001</h1>
        <p>Due: March 15, 2024</p>
    </div>
    <table class='invoice-table'>
        <tr><th>Item</th><th>Quantity</th><th>Unit Price</th><th>Total</th></tr>
        <tr><td>PDF License</td><td>1</td><td>$599</td><td>$599</td></tr>
        <tr><td>Support Package</td><td>1</td><td>$199</td><td>$199</td></tr>
    </table>
    <p class='total'>Grand Total: $798</p>
";

var renderer = new ChromePdfRenderer();
var pdfDocument = renderer.RenderHtmlAsPdf(html);
var pdfBytes = pdfDocument.BinaryData;

using IronPdf;

var html = @"
    <style>
        body { font-family: Arial, sans-serif; margin: 0; }
        .invoice-header { background: #4CAF50; color: white; padding: 20px; }
        .invoice-table { width: 100%; border-collapse: collapse; margin-top: 20px; }
        .invoice-table th, .invoice-table td {
            border: 1px solid #ddd; padding: 8px; text-align: left;
        }
        .invoice-table th { background-color: #f2f2f2; }
        .total { font-size: 18px; font-weight: bold; margin-top: 16px; }
    </style>
    <div class='invoice-header'>
        <h1>Invoice #2024-001</h1>
        <p>Due: March 15, 2024</p>
    </div>
    <table class='invoice-table'>
        <tr><th>Item</th><th>Quantity</th><th>Unit Price</th><th>Total</th></tr>
        <tr><td>PDF License</td><td>1</td><td>$599</td><td>$599</td></tr>
        <tr><td>Support Package</td><td>1</td><td>$199</td><td>$199</td></tr>
    </table>
    <p class='total'>Grand Total: $798</p>
";

var renderer = new ChromePdfRenderer();
var pdfDocument = renderer.RenderHtmlAsPdf(html);
var pdfBytes = pdfDocument.BinaryData;

using iTextSharp.text;
using iTextSharp.text.pdf;

var output = new MemoryStream();
var document = new Document(PageSize.A4);
PdfWriter.GetInstance(document, output);
document.Open();

// Header -- manual font and color setup
var titleFont = FontFactory.GetFont(FontFactory.HELVETICA_BOLD, 20,
    new BaseColor(255, 255, 255));
var headerParagraph = new Paragraph("Invoice #2024-001", titleFont);
document.Add(headerParagraph);

// Table -- each cell must be created individually
PdfPTable table = new PdfPTable(4);
table.WidthPercentage = 100;

string[] headers = { "Item", "Quantity", "Unit Price", "Total" };
foreach (var h in headers)
{
    var cell = new PdfPCell(new Phrase(h,
        FontFactory.GetFont(FontFactory.HELVETICA_BOLD, 10)));
    cell.BackgroundColor = new BaseColor(242, 242, 242);
    table.AddCell(cell);
}

table.AddCell("PDF License");
table.AddCell("1");
table.AddCell("$599");
table.AddCell("$599");
document.Add(table);

var totalFont = FontFactory.GetFont(FontFactory.HELVETICA_BOLD, 14);
document.Add(new Paragraph("Grand Total: $798", totalFont));
document.Close();

using iTextSharp.text;
using iTextSharp.text.pdf;

var output = new MemoryStream();
var document = new Document(PageSize.A4);
PdfWriter.GetInstance(document, output);
document.Open();

// Header -- manual font and color setup
var titleFont = FontFactory.GetFont(FontFactory.HELVETICA_BOLD, 20,
    new BaseColor(255, 255, 255));
var headerParagraph = new Paragraph("Invoice #2024-001", titleFont);
document.Add(headerParagraph);

// Table -- each cell must be created individually
PdfPTable table = new PdfPTable(4);
table.WidthPercentage = 100;

string[] headers = { "Item", "Quantity", "Unit Price", "Total" };
foreach (var h in headers)
{
    var cell = new PdfPCell(new Phrase(h,
        FontFactory.GetFont(FontFactory.HELVETICA_BOLD, 10)));
    cell.BackgroundColor = new BaseColor(242, 242, 242);
    table.AddCell(cell);
}

table.AddCell("PDF License");
table.AddCell("1");
table.AddCell("$599");
table.AddCell("$599");
document.Add(table);

var totalFont = FontFactory.GetFont(FontFactory.HELVETICA_BOLD, 14);
document.Add(new Paragraph("Grand Total: $798", totalFont));
document.Close();

How Do You Handle Server-Side PDF Generation in ASP.NET?

Both libraries support server-side PDF generation for ASP.NET applications. The pattern for returning a PDF as a downloadable file response is similar regardless of which library generates the bytes. The key considerations for production use are memory management, thread safety, and response configuration. Both libraries use in-memory streams, so you should ensure you are not holding large PDFs in memory longer than necessary. IronPDF's ChromePdfRenderer is designed to be instantiated per request, so there is no shared state to worry about between concurrent requests.

using IronPdf;
using Microsoft.AspNetCore.Mvc;

[ApiController]
[Route("api/[controller]")]
public class PdfController : ControllerBase
{
    [HttpGet("invoice/{id}")]
    public IActionResult GenerateInvoice(int id)
    {
        var html = BuildInvoiceHtml(id); // your HTML template

        var renderer = new ChromePdfRenderer();
        renderer.RenderingOptions.PaperSize = IronPdf.Rendering.PdfPaperSize.A4;
        renderer.RenderingOptions.MarginTop = 20;
        renderer.RenderingOptions.MarginBottom = 20;

        var pdf = renderer.RenderHtmlAsPdf(html);

        return File(pdf.BinaryData, "application/pdf", $"invoice-{id}.pdf");
    }

    private static string BuildInvoiceHtml(int id)
    {
        return $"<h1>Invoice #{id}</h1><p>Generated on {DateTime.UtcNow:yyyy-MM-dd}</p>";
    }
}

using IronPdf;
using Microsoft.AspNetCore.Mvc;

[ApiController]
[Route("api/[controller]")]
public class PdfController : ControllerBase
{
    [HttpGet("invoice/{id}")]
    public IActionResult GenerateInvoice(int id)
    {
        var html = BuildInvoiceHtml(id); // your HTML template

        var renderer = new ChromePdfRenderer();
        renderer.RenderingOptions.PaperSize = IronPdf.Rendering.PdfPaperSize.A4;
        renderer.RenderingOptions.MarginTop = 20;
        renderer.RenderingOptions.MarginBottom = 20;

        var pdf = renderer.RenderHtmlAsPdf(html);

        return File(pdf.BinaryData, "application/pdf", $"invoice-{id}.pdf");
    }

    private static string BuildInvoiceHtml(int id)
    {
        return $"<h1>Invoice #{id}</h1><p>Generated on {DateTime.UtcNow:yyyy-MM-dd}</p>";
    }
}

How Do You Migrate from iTextSharp to IronPDF?

Migrating an existing iTextSharp project to IronPDF follows a straightforward pattern:

1. Replace document model code with HTML templates. Instead of constructing Paragraph, PdfPTable, and PdfPCell objects, build an HTML string or load an HTML file. Your existing CSS stylesheets and Razor partial views can be reused directly.
2. Swap the rendering call. Replace PdfWriter.GetInstance(doc, stream) with new ChromePdfRenderer().RenderHtmlAsPdf(html).
3. Update the byte extraction. Replace memoryStream.ToArray() with pdf.BinaryData.
4. Transfer advanced settings. iTextSharp features like page margins, encryption, and document metadata have direct equivalents in IronPDF's RenderingOptions and PdfDocument APIs.
5. Validate output fidelity. Run both outputs side-by-side on representative documents. IronPDF typically produces better visual results because it uses a full browser rendering engine rather than a PDF-native layout engine.

For teams with existing HTML templates (from email generators, Razor views, or report builders), migration can often be completed in hours rather than days. IronPDF can render Razor views directly to PDF within ASP.NET Core, which further accelerates migration. Teams that have invested in CSS-based document design -- for example, using print stylesheets to control page breaks and margins -- will find those skills transfer directly to IronPDF.

Review the IronPDF migration guide for detailed patterns covering encryption, stamping, and other advanced iTextSharp features.

Which Library Should You Choose?

For developers starting new projects or migrating from iTextSharp, the following factors apply:

Licensing: iTextSharp uses AGPL licensing for its newer versions, which requires either open-sourcing your application or purchasing a commercial license from iText Group. IronPDF offers straightforward commercial licensing with no open-source obligations. If your project is closed-source or commercial, this distinction alone may determine your choice.

Learning Curve: IronPDF's HTML-based approach means less time learning PDF-specific APIs. If your team knows HTML and CSS, PDF generation with IronPDF starts immediately. There is no need to study PDF coordinate systems, glyph encoding, or font embedding -- IronPDF handles all of that transparently.

Feature Coverage: IronPDF supports PDF/A compliance, form filling, watermarking, , and more -- all from a single NuGet package. Advanced features like digital signatures and PDF merging are also included without additional dependencies.

Migration Path: Moving from iTextSharp to IronPDF involves replacing document-manipulation code with HTML templates and updating the rendering call. The output quality is typically higher because IronPDF uses a full browser engine, and the resulting code is significantly shorter and easier to maintain.

For background on how PDF rendering engines work and what differentiates them, Mozilla's documentation on PDFs and Adobe's PDF specification resources provide useful context. The iText Group official site describes the AGPL terms in detail.

What Are Your Next Steps?

To get started with IronPDF in your ASP.NET project:

1. Install the NuGet package: Install-Package IronPdf
2. Add using IronPdf; to your file
3. Create a ChromePdfRenderer and call RenderHtmlAsPdf() with your HTML
4. Return pdf.BinaryData as a FileResult from your controller

Explore these resources to go further:

• IronPDF HTML to PDF documentation -- full rendering options and examples
• ASP.NET Core PDF generation guide -- Razor view rendering and controller patterns
• PDF security and encryption -- password protection and permissions
• PDF merging and splitting -- combining multiple documents
• IronPDF free trial -- test all features without a watermark during development