COMPARISON

ZetPDF vs IronPDF: Technical Comparison Guide

Published:

When .NET developers evaluate PDF libraries for document generation and manipulation, ZetPDF appears as a commercially licensed option built on the PDFSharp foundation. However, its inherited architecture and limitations raise important considerations for teams building modern applications. This technical comparison examines ZetPDF alongside IronPDF to help architects and developers understand the fundamental differences in rendering technology, API design, and feature completeness.

Understanding ZetPDF

ZetPDF is a commercially licensed PDF library designed for handling PDF files within C# applications. Built on the foundation of the widely used open-source PDFSharp library, ZetPDF provides a robust solution for creating, modifying, and managing PDF documents with commercial support and licensing options.

As a PDFSharp-based library, ZetPDF inherits both the capabilities and constraints of its foundation:

  • PDFSharp Foundation: Leverages PDFSharp's core capabilities with commercial licensing
  • Coordinate-Based API: Requires manual positioning of elements with exact coordinates
  • Commercial Support: Provides prioritized support through commercial licensing
  • Flexible Licensing: Offers developer, project, or OEM licensing models
  • Inherited Limitations: Inherits PDFSharp's constraints, including limited HTML-to-PDF capabilities

The PDFSharp Heritage

ZetPDF's coordinate-based programming model forces developers to position every element manually:

// ZetPDF: Manual positioning with coordinates
graphics.DrawString("Name:", font, brush, new XPoint(50, 100));
graphics.DrawString("John Doe", font, brush, new XPoint(100, 100));
graphics.DrawString("Address:", font, brush, new XPoint(50, 120));
graphics.DrawString("123 Main St", font, brush, new XPoint(100, 120));
// ... hundreds of lines for a simple form
// ZetPDF: Manual positioning with coordinates
graphics.DrawString("Name:", font, brush, new XPoint(50, 100));
graphics.DrawString("John Doe", font, brush, new XPoint(100, 100));
graphics.DrawString("Address:", font, brush, new XPoint(50, 120));
graphics.DrawString("123 Main St", font, brush, new XPoint(100, 120));
// ... hundreds of lines for a simple form
$vbLabelText   $csharpLabel

This approach can become complex for document layouts that need to adapt to varying content lengths or require responsive design patterns.

Understanding IronPDF

IronPDF takes a fundamentally different approach, using Chromium-based technology to deliver HTML-to-PDF conversion with full web standards support. Rather than coordinate-based graphics programming, IronPDF enables developers to use familiar HTML and CSS for document creation.

Key characteristics include:

  • Chromium Rendering Engine: Uses modern browser technology for accurate HTML/CSS rendering
  • HTML/CSS-Based Design: Leverages web development skills for document layout
  • Full JavaScript Support: Renders dynamic web content with ES2024 JavaScript
  • Automatic Layout: Content flows naturally without manual coordinate calculations
  • Advanced PDF Features: Built-in support for watermarks, headers/footers, merging, and more

Feature Comparison

The following table highlights the key differences between ZetPDF and IronPDF based on their architectural approaches:

FeatureZetPDFIronPDF
Based on PDFSharpYesNo
HTML-to-PDF ConversionLimitedYes (Full Chromium rendering)
Commercial LicenseYes, PerpetualYes
Open Source FoundationPDFSharp (MIT License)Chromium-based
Differentiation from PDFSharpLimitedFull HTML-to-PDF, unique capabilities
Simplicity and Ease of UseModerateHigh
Support for PDF AnnotationsYesYes
Text ExtractionStandardAdvanced
Watermarking SupportYesYes

Detailed Feature Comparison

FeatureZetPDFIronPDF
Content Creation
HTML to PDFLimitedYes
URL to PDFLimitedYes
CSS SupportNoFull CSS3
JavaScriptNoFull ES2024
Layout
Automatic LayoutNoYes
Auto Page BreaksNoYes
TablesManual drawingHTML <table>
ImagesManual placement<img> tag
PDF Operations
Headers/FootersManualHTML/CSS
WatermarksManual codeBuilt-in
Merge PDFsYesYes
Split PDFsLimitedYes
Digital SignaturesNoYes
PDF/ANoYes
Development
Cross-PlatformYesYes

API Architecture Differences

The API patterns between ZetPDF and IronPDF reveal different design philosophies around PDF generation.

ZetPDF HtmlToPdfConverter Pattern

ZetPDF provides an HtmlToPdfConverter class for HTML-to-PDF conversion:

// NuGet: Install-Package ZetPDF
using ZetPDF;
using System;

class Program
{
    static void Main()
    {
        var converter = new HtmlToPdfConverter();
        var htmlContent = "<html><body><h1>Hello World</h1></body></html>";
        converter.ConvertHtmlToPdf(htmlContent, "output.pdf");
        Console.WriteLine("PDF created successfully");
    }
}
// NuGet: Install-Package ZetPDF
using ZetPDF;
using System;

class Program
{
    static void Main()
    {
        var converter = new HtmlToPdfConverter();
        var htmlContent = "<html><body><h1>Hello World</h1></body></html>";
        converter.ConvertHtmlToPdf(htmlContent, "output.pdf");
        Console.WriteLine("PDF created successfully");
    }
}
$vbLabelText   $csharpLabel

The ConvertHtmlToPdf method takes HTML content and an output file path, writing the result directly to disk.

IronPDF ChromePdfRenderer Pattern

IronPDF uses the ChromePdfRenderer class with Chromium-based rendering:

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

class Program
{
    static void Main()
    {
        var renderer = new ChromePdfRenderer();
        var htmlContent = "<html><body><h1>Hello World</h1></body></html>";
        var pdf = renderer.RenderHtmlAsPdf(htmlContent);
        pdf.SaveAs("output.pdf");
        Console.WriteLine("PDF created successfully");
    }
}
// NuGet: Install-Package IronPdf
using IronPdf;
using System;

class Program
{
    static void Main()
    {
        var renderer = new ChromePdfRenderer();
        var htmlContent = "<html><body><h1>Hello World</h1></body></html>";
        var pdf = renderer.RenderHtmlAsPdf(htmlContent);
        pdf.SaveAs("output.pdf");
        Console.WriteLine("PDF created successfully");
    }
}
$vbLabelText   $csharpLabel

The ChromePdfRenderer returns a PdfDocument object that provides additional manipulation capabilities before saving. For comprehensive HTML conversion guidance, see the HTML to PDF tutorial.

URL to PDF Conversion

Converting live web pages to PDF documents demonstrates the capabilities of each library's web rendering approach.

ZetPDF Implementation

ZetPDF provides URL conversion through its HtmlToPdfConverter class:

// NuGet: Install-Package ZetPDF
using ZetPDF;
using System;

class Program
{
    static void Main()
    {
        var converter = new HtmlToPdfConverter();
        var url = "https://www.example.com";
        converter.ConvertUrlToPdf(url, "webpage.pdf");
        Console.WriteLine("PDF from URL created successfully");
    }
}
// NuGet: Install-Package ZetPDF
using ZetPDF;
using System;

class Program
{
    static void Main()
    {
        var converter = new HtmlToPdfConverter();
        var url = "https://www.example.com";
        converter.ConvertUrlToPdf(url, "webpage.pdf");
        Console.WriteLine("PDF from URL created successfully");
    }
}
$vbLabelText   $csharpLabel

IronPDF Implementation

IronPDF provides dedicated URL rendering with Chromium:

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

class Program
{
    static void Main()
    {
        var renderer = new ChromePdfRenderer();
        var url = "https://www.example.com";
        var pdf = renderer.RenderUrlAsPdf(url);
        pdf.SaveAs("webpage.pdf");
        Console.WriteLine("PDF from URL created successfully");
    }
}
// NuGet: Install-Package IronPdf
using IronPdf;
using System;

class Program
{
    static void Main()
    {
        var renderer = new ChromePdfRenderer();
        var url = "https://www.example.com";
        var pdf = renderer.RenderUrlAsPdf(url);
        pdf.SaveAs("webpage.pdf");
        Console.WriteLine("PDF from URL created successfully");
    }
}
$vbLabelText   $csharpLabel

The RenderUrlAsPdf method leverages Chromium's rendering engine to process web pages with full JavaScript execution and modern CSS support, producing output that matches what users see in modern browsers.

PDF Merging Operations

Combining multiple PDF documents is a common requirement for document assembly workflows.

ZetPDF Merger Pattern

ZetPDF provides a PdfMerger class for combining documents:

// NuGet: Install-Package ZetPDF
using ZetPDF;
using System;
using System.Collections.Generic;

class Program
{
    static void Main()
    {
        var merger = new PdfMerger();
        var files = new List<string> { "document1.pdf", "document2.pdf" };
        merger.MergeFiles(files, "merged.pdf");
        Console.WriteLine("PDFs merged successfully");
    }
}
// NuGet: Install-Package ZetPDF
using ZetPDF;
using System;
using System.Collections.Generic;

class Program
{
    static void Main()
    {
        var merger = new PdfMerger();
        var files = new List<string> { "document1.pdf", "document2.pdf" };
        merger.MergeFiles(files, "merged.pdf");
        Console.WriteLine("PDFs merged successfully");
    }
}
$vbLabelText   $csharpLabel

The MergeFiles method accepts a list of file paths and an output path, writing the merged result directly to disk.

IronPDF Static Merge Pattern

IronPDF provides a static Merge method on the PdfDocument class:

// NuGet: Install-Package IronPdf
using IronPdf;
using System;
using System.Collections.Generic;

class Program
{
    static void Main()
    {
        var pdfs = new List<PdfDocument>
        {
            PdfDocument.FromFile("document1.pdf"),
            PdfDocument.FromFile("document2.pdf")
        };
        var merged = PdfDocument.Merge(pdfs);
        merged.SaveAs("merged.pdf");
        Console.WriteLine("PDFs merged successfully");
    }
}
// NuGet: Install-Package IronPdf
using IronPdf;
using System;
using System.Collections.Generic;

class Program
{
    static void Main()
    {
        var pdfs = new List<PdfDocument>
        {
            PdfDocument.FromFile("document1.pdf"),
            PdfDocument.FromFile("document2.pdf")
        };
        var merged = PdfDocument.Merge(pdfs);
        merged.SaveAs("merged.pdf");
        Console.WriteLine("PDFs merged successfully");
    }
}
$vbLabelText   $csharpLabel

The PdfDocument.Merge method returns a PdfDocument object, enabling additional operations like watermarking, security settings, or metadata modification before saving.

API Mapping Reference

Teams evaluating a transition from ZetPDF to IronPDF will find this mapping helpful for understanding concept equivalences:

ZetPDFIronPDF
new HtmlToPdfConverter()new ChromePdfRenderer()
converter.ConvertHtmlToPdf()renderer.RenderHtmlAsPdf()
converter.ConvertUrlToPdf()renderer.RenderUrlAsPdf()
new PdfMerger()PdfDocument.Merge()
merger.MergeFiles()PdfDocument.Merge(list)
new PdfDocument()new ChromePdfRenderer()
document.AddPage()Automatic
XGraphics.FromPdfPage(page)N/A
graphics.DrawString()HTML text elements
graphics.DrawImage()<img> tag
graphics.DrawLine()CSS borders
graphics.DrawRectangle()CSS border + div
new XFont()CSS font-family
XBrushes.BlackCSS color
document.Save()pdf.SaveAs()
PdfReader.Open()PdfDocument.FromFile()

Coordinate-Based vs HTML-Based Design

The fundamental architectural difference between ZetPDF and IronPDF lies in their approach to document layout.

ZetPDF Graphics Programming

ZetPDF's PDFSharp foundation requires coordinate-based positioning:

using ZetPdf;
using ZetPdf.Drawing;

var document = new PdfDocument();
var page = document.AddPage();
var graphics = XGraphics.FromPdfPage(page);
var titleFont = new XFont("Arial", 24, XFontStyle.Bold);
var bodyFont = new XFont("Arial", 12);

graphics.DrawString("Company Report", titleFont, XBrushes.Navy,
    new XPoint(50, 50));
graphics.DrawString("This is the introduction paragraph.", bodyFont, XBrushes.Black,
    new XPoint(50, 80));
graphics.DrawString("Generated: " + DateTime.Now.ToString(), bodyFont, XBrushes.Gray,
    new XPoint(50, 100));

document.Save("report.pdf");
using ZetPdf;
using ZetPdf.Drawing;

var document = new PdfDocument();
var page = document.AddPage();
var graphics = XGraphics.FromPdfPage(page);
var titleFont = new XFont("Arial", 24, XFontStyle.Bold);
var bodyFont = new XFont("Arial", 12);

graphics.DrawString("Company Report", titleFont, XBrushes.Navy,
    new XPoint(50, 50));
graphics.DrawString("This is the introduction paragraph.", bodyFont, XBrushes.Black,
    new XPoint(50, 80));
graphics.DrawString("Generated: " + DateTime.Now.ToString(), bodyFont, XBrushes.Gray,
    new XPoint(50, 100));

document.Save("report.pdf");
$vbLabelText   $csharpLabel

This approach requires creating font objects, brush objects, and specifying exact X,Y coordinates for every element.

IronPDF HTML/CSS Design

IronPDF uses familiar web technologies:

using IronPdf;

var html = $@"
<html>
<head>
    <style>
        body {{ font-family: Arial, sans-serif; padding: 50px; }}
        h1 {{ color: navy; }}
        .date {{ color: gray; }}
    </style>
</head>
<body>
    <h1>Company Report</h1>
    <p>This is the introduction paragraph.</p>
    <p class='date'>Generated: {DateTime.Now}</p>
</body>
</html>";

var renderer = new ChromePdfRenderer();
renderer.RenderingOptions.PaperSize = PdfPaperSize.A4;
var pdf = renderer.RenderHtmlAsPdf(html);
pdf.SaveAs("report.pdf");
using IronPdf;

var html = $@"
<html>
<head>
    <style>
        body {{ font-family: Arial, sans-serif; padding: 50px; }}
        h1 {{ color: navy; }}
        .date {{ color: gray; }}
    </style>
</head>
<body>
    <h1>Company Report</h1>
    <p>This is the introduction paragraph.</p>
    <p class='date'>Generated: {DateTime.Now}</p>
</body>
</html>";

var renderer = new ChromePdfRenderer();
renderer.RenderingOptions.PaperSize = PdfPaperSize.A4;
var pdf = renderer.RenderHtmlAsPdf(html);
pdf.SaveAs("report.pdf");
$vbLabelText   $csharpLabel

HTML handles layout automatically—CSS provides styling without font object management, and content flows naturally across pages.

When Teams Consider Moving from ZetPDF to IronPDF

Several scenarios commonly prompt development teams to evaluate IronPDF as an alternative to ZetPDF:

Modern Web Content Requirements

Teams building applications that generate PDFs from web-based templates, dashboards, or reports find coordinate-based approaches limiting. IronPDF's Chromium engine renders modern CSS Grid, Flexbox, and JavaScript-driven content that coordinate-based libraries cannot fully support.

HTML/CSS Developer Skills

Teams with strong web development skills find the learning curve for coordinate-based PDF generation steep. HTML and CSS are widely understood technologies, making IronPDF's approach more accessible to developers without specialized PDF or graphics programming expertise.

Reduced Code Complexity

The coordinate-based API produces verbose code that becomes difficult to maintain as document layouts evolve. A simple report might require dozens of DrawString and coordinate calculations in ZetPDF versus a few lines of HTML/CSS with IronPDF.

Automatic Page Breaks and Layout

ZetPDF requires manual tracking of Y positions and explicit page creation when content exceeds page boundaries. IronPDF handles page breaks automatically based on CSS rules and content flow:

// IronPDF - automatic page breaks
var html = @"
<div>Page 1 content</div>
<div style='page-break-after: always;'></div>
<div>Page 2 content</div>";

var renderer = new ChromePdfRenderer();
var pdf = renderer.RenderHtmlAsPdf(html);
pdf.SaveAs("multipage.pdf");
// IronPDF - automatic page breaks
var html = @"
<div>Page 1 content</div>
<div style='page-break-after: always;'></div>
<div>Page 2 content</div>";

var renderer = new ChromePdfRenderer();
var pdf = renderer.RenderHtmlAsPdf(html);
pdf.SaveAs("multipage.pdf");
$vbLabelText   $csharpLabel

Advanced PDF Features

IronPDF provides built-in support for features that require manual implementation or external tools with ZetPDF:

Strengths and Considerations

ZetPDF Strengths

  • Commercial Support: Provides prioritized support through commercial licensing, ensuring developers receive timely assistance
  • PDFSharp Integration: Leverages PDFSharp's core capabilities, recognized by many .NET developers
  • Flexible Licensing: Allows flexibility in licensing models tailored to developer, project, or OEM needs
  • Cross-Platform: Supports multiple platforms for deployment flexibility

ZetPDF Considerations

  • Inherited Limitations: As ZetPDF is based on PDFSharp, it inherits constraints from the underlying library
  • Limited Differentiation: Compared to using PDFSharp directly, ZetPDF offers limited compelling reasons for its commercial licensing
  • Coordinate-Based Complexity: Manual positioning requirements increase code complexity for dynamic documents

IronPDF Strengths

  • Complete HTML-to-PDF Solution: Comprehensive HTML-to-PDF functionality essential for automating web page conversions
  • Enhanced Rendering: Chromium-based rendering provides superior web content processing, directly affecting output quality
  • Advanced Features: Unique capabilities including PDF forms management, dynamic watermarking, and digital signatures extend beyond standard PDF manipulations
  • Active Development: Regular updates ensure compatibility with modern .NET versions

.NET Compatibility and Future Readiness

Both libraries support cross-platform .NET development. IronPDF maintains active development with regular updates, ensuring compatibility with .NET 8, .NET 9, and future releases including .NET 10 expected in 2026. The library's HTML/CSS approach aligns with modern web development practices, leveraging skills that .NET developers already possess through their familiarity with web technologies.

Conclusion

ZetPDF and IronPDF represent different approaches to PDF generation in .NET. ZetPDF, with its PDFSharp foundation, provides a reliable solution for developers familiar with coordinate-based graphics programming. Its commercial licensing offers support and reliability for teams invested in the PDFSharp ecosystem.

IronPDF's Chromium-based approach treats PDF generation as web rendering, enabling developers to use HTML, CSS, and JavaScript rather than learning coordinate-based graphics APIs. Automatic layout, page breaks, and modern web standards support (CSS Grid, Flexbox, ES2024 JavaScript) significantly reduce code complexity while producing output that matches modern browser rendering.

For teams building applications that generate web-based reports, dashboards, or dynamic documents, IronPDF's approach aligns naturally with modern development practices. For teams with existing PDFSharp expertise or specific requirements around low-level PDF control, ZetPDF's commercial offering provides support and licensing options around the familiar PDFSharp foundation.

The choice ultimately depends on your team's requirements: if your PDFs originate from web content or you prefer HTML/CSS for document design, IronPDF offers significant productivity advantages. If you're building on existing PDFSharp skills or require the specific licensing models ZetPDF provides, that path may suit your needs.

For additional implementation guidance, explore the IronPDF documentation and tutorials covering specific use cases and advanced features.