COMPARISON

Telerik Document Processing vs IronPDF: Technical Comparison Guide

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Understanding Telerik Document Processing

Telerik Document Processing is part of the broader Telerik suite, known for providing comprehensive UI components and solutions for .NET application development. As a commercial offering under the DevCraft license, it enables developers to integrate PDF processing abilities directly within their projects.

The library uses a Flow Document architecture that converts HTML to an intermediate RadFlowDocument model before generating PDF output. This approach requires multiple format providers (HtmlFormatProvider, PdfFormatProvider) and explicit document model manipulation.

Telerik Document Processing offers features for not just PDF generation, but also for managing various document formats like Word, Excel, and PowerPoint, providing flexibility beyond PDFs for organizations already invested in the Telerik ecosystem.

Understanding IronPDF

IronPDF provides a modern, standalone PDF library that simplifies HTML-to-PDF conversion using a Chromium rendering engine. The library provides robust support for HTML5, CSS3, and JavaScript, ensuring fidelity in document rendering across modern web standards.

IronPDF uses a direct rendering approach without intermediate document models, converting HTML content to PDF in a single step. This architectural simplicity translates to fewer lines of code and reduced API complexity.

The CSS/HTML Rendering Problem

One of the most significant technical differences between these libraries lies in how they handle modern HTML and CSS.

Telerik Document Processing CSS Limitations

Telerik Document Processing has fundamental issues when handling modern HTML/CSS. The library converts HTML to an intermediate Flow Document model, which:

  • Flattens HTML structure — <div> elements become paragraphs
  • Ignores modern CSS — Flexbox and Grid layouts fail
  • Breaks Bootstrap — Column systems don't work correctly
  • Loses formatting — Complex selectors are ignored

Developers have voiced concerns regarding the library's inability to fully support modern CSS standards. CSS3 constructs and Bootstrap layouts face compatibility issues, leading to significant changes in layout and rendering.

IronPDF Chromium Engine

IronPDF uses a Chromium-based rendering engine that handles complex stylesheets, external CSS files, and responsive designs exactly as they appear in browsers. This includes full support for:

  • CSS3 features including Flexbox and Grid
  • Bootstrap 5 layouts
  • CSS Variables
  • Complex selectors
  • Modern units like calc() and rem

Feature Comparison Overview

Feature / CriteriaTelerik Document ProcessingIronPDF
HTML/CSS SupportLimited, Issues with Bootstrap and CSS3Full, including Bootstrap 5
HTML RenderingFlow Document conversionDirect Chromium rendering
CSS3 SupportLimited, many features failFull CSS3
FlexboxNot supportedSupported
CSS GridNot supportedSupported
BootstrapBroken (div flattening)Supported
JavaScriptNot supportedSupported
File PerformanceOutOfMemoryException on large filesStable and efficient
License ModelCommercial, part of DevCraftSimple standalone licensing
API ComplexityComplex (providers, models)Simple (one class)

HTML to PDF Conversion

HTML-to-PDF conversion reveals the fundamental architectural differences between these libraries.

Telerik Document Processing HTML to PDF

Telerik requires multiple format providers and explicit document model handling:

// NuGet: Install-Package Telerik.Documents.Flow
// NuGet: Install-Package Telerik.Documents.Flow.FormatProviders.Pdf
using Telerik.Windows.Documents.Flow.FormatProviders.Html;
using Telerik.Windows.Documents.Flow.FormatProviders.Pdf;
using Telerik.Windows.Documents.Flow.Model;
using System.IO;

string html = "<html><body><h1>Hello World</h1><p>This is a PDF document.</p></body></html>";

HtmlFormatProvider htmlProvider = new HtmlFormatProvider();
RadFlowDocument document = htmlProvider.Import(html);

PdfFormatProvider pdfProvider = new PdfFormatProvider();
using (FileStream output = File.OpenWrite("output.pdf"))
{
    pdfProvider.Export(document, output);
}
// NuGet: Install-Package Telerik.Documents.Flow
// NuGet: Install-Package Telerik.Documents.Flow.FormatProviders.Pdf
using Telerik.Windows.Documents.Flow.FormatProviders.Html;
using Telerik.Windows.Documents.Flow.FormatProviders.Pdf;
using Telerik.Windows.Documents.Flow.Model;
using System.IO;

string html = "<html><body><h1>Hello World</h1><p>This is a PDF document.</p></body></html>";

HtmlFormatProvider htmlProvider = new HtmlFormatProvider();
RadFlowDocument document = htmlProvider.Import(html);

PdfFormatProvider pdfProvider = new PdfFormatProvider();
using (FileStream output = File.OpenWrite("output.pdf"))
{
    pdfProvider.Export(document, output);
}
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This approach requires:

  • Multiple NuGet packages (Telerik.Documents.Flow, Telerik.Documents.Flow.FormatProviders.Pdf)
  • Creating HtmlFormatProvider to import HTML into RadFlowDocument
  • Creating separate PdfFormatProvider for PDF export
  • Manual FileStream management
  • Understanding the Flow Document intermediate model

IronPDF HTML to PDF

IronPDF provides direct HTML-to-PDF conversion:

// NuGet: Install-Package IronPdf
using IronPdf;

string html = "<html><body><h1>Hello World</h1><p>This is a PDF document.</p></body></html>";

var renderer = new ChromePdfRenderer();
var pdf = renderer.RenderHtmlAsPdf(html);
pdf.SaveAs("output.pdf");
// NuGet: Install-Package IronPdf
using IronPdf;

string html = "<html><body><h1>Hello World</h1><p>This is a PDF document.</p></body></html>";

var renderer = new ChromePdfRenderer();
var pdf = renderer.RenderHtmlAsPdf(html);
pdf.SaveAs("output.pdf");
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The RenderHtmlAsPdf method converts HTML content directly to PDF using the Chromium rendering engine. No intermediate document models, no multiple providers, no manual stream management—the entire operation completes in three lines of code.

URL to PDF Conversion

Converting web pages to PDF demonstrates a critical capability gap.

Telerik Document Processing URL to PDF

Telerik Document Processing does not provide native URL-to-PDF conversion. Developers must manually download HTML content before processing:

// NuGet: Install-Package Telerik.Documents.Flow
// NuGet: Install-Package Telerik.Documents.Flow.FormatProviders.Pdf
using Telerik.Windows.Documents.Flow.FormatProviders.Html;
using Telerik.Windows.Documents.Flow.FormatProviders.Pdf;
using Telerik.Windows.Documents.Flow.Model;
using System.IO;
using System.Net.Http;
using System.Threading.Tasks;

string url = "https://example.com";

using HttpClient client = new HttpClient();
string html = await client.GetStringAsync(url);

HtmlFormatProvider htmlProvider = new HtmlFormatProvider();
RadFlowDocument document = htmlProvider.Import(html);

PdfFormatProvider pdfProvider = new PdfFormatProvider();
using (FileStream output = File.OpenWrite("webpage.pdf"))
{
    pdfProvider.Export(document, output);
}
// NuGet: Install-Package Telerik.Documents.Flow
// NuGet: Install-Package Telerik.Documents.Flow.FormatProviders.Pdf
using Telerik.Windows.Documents.Flow.FormatProviders.Html;
using Telerik.Windows.Documents.Flow.FormatProviders.Pdf;
using Telerik.Windows.Documents.Flow.Model;
using System.IO;
using System.Net.Http;
using System.Threading.Tasks;

string url = "https://example.com";

using HttpClient client = new HttpClient();
string html = await client.GetStringAsync(url);

HtmlFormatProvider htmlProvider = new HtmlFormatProvider();
RadFlowDocument document = htmlProvider.Import(html);

PdfFormatProvider pdfProvider = new PdfFormatProvider();
using (FileStream output = File.OpenWrite("webpage.pdf"))
{
    pdfProvider.Export(document, output);
}
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This workaround approach:

  • Requires manual HttpClient setup and HTTP request handling
  • Downloads only static HTML (no JavaScript execution)
  • Cannot render dynamic content or SPAs
  • External stylesheets may not be properly resolved
  • Adds complexity and potential points of failure

IronPDF URL to PDF

IronPDF provides native URL-to-PDF conversion:

// NuGet: Install-Package IronPdf
using IronPdf;

string url = "https://example.com";

var renderer = new ChromePdfRenderer();
var pdf = renderer.RenderUrlAsPdf(url);
pdf.SaveAs("webpage.pdf");
// NuGet: Install-Package IronPdf
using IronPdf;

string url = "https://example.com";

var renderer = new ChromePdfRenderer();
var pdf = renderer.RenderUrlAsPdf(url);
pdf.SaveAs("webpage.pdf");
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The RenderUrlAsPdf method navigates to the URL using the Chromium engine, executes JavaScript, renders the complete page, and captures the result. No manual HTTP handling, no missing dynamic content, no CSS resolution issues.

PDF Merging Operations

Combining multiple PDF documents demonstrates significant differences in API complexity.

Telerik Document Processing PDF Merge

Telerik requires manual page iteration and document model handling:

// NuGet: Install-Package Telerik.Documents.Fixed
using Telerik.Windows.Documents.Fixed.FormatProviders.Pdf;
using Telerik.Windows.Documents.Fixed.Model;
using System.IO;

PdfFormatProvider provider = new PdfFormatProvider();

RadFixedDocument document1;
using (FileStream input = File.OpenRead("document1.pdf"))
{
    document1 = provider.Import(input);
}

RadFixedDocument document2;
using (FileStream input = File.OpenRead("document2.pdf"))
{
    document2 = provider.Import(input);
}

RadFixedDocument mergedDocument = new RadFixedDocument();
foreach (var page in document1.Pages)
{
    mergedDocument.Pages.Add(page);
}
foreach (var page in document2.Pages)
{
    mergedDocument.Pages.Add(page);
}

using (FileStream output = File.OpenWrite("merged.pdf"))
{
    provider.Export(mergedDocument, output);
}
// NuGet: Install-Package Telerik.Documents.Fixed
using Telerik.Windows.Documents.Fixed.FormatProviders.Pdf;
using Telerik.Windows.Documents.Fixed.Model;
using System.IO;

PdfFormatProvider provider = new PdfFormatProvider();

RadFixedDocument document1;
using (FileStream input = File.OpenRead("document1.pdf"))
{
    document1 = provider.Import(input);
}

RadFixedDocument document2;
using (FileStream input = File.OpenRead("document2.pdf"))
{
    document2 = provider.Import(input);
}

RadFixedDocument mergedDocument = new RadFixedDocument();
foreach (var page in document1.Pages)
{
    mergedDocument.Pages.Add(page);
}
foreach (var page in document2.Pages)
{
    mergedDocument.Pages.Add(page);
}

using (FileStream output = File.OpenWrite("merged.pdf"))
{
    provider.Export(mergedDocument, output);
}
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This approach requires:

  • PdfFormatProvider for import and export operations
  • Separate FileStream objects for each document
  • Manual iteration through page collections
  • Creating a new RadFixedDocument for the merged result
  • Explicit Pages.Add() calls for each page
  • Complex resource management with multiple using statements

IronPDF PDF Merge

IronPDF provides a declarative merge operation:

// NuGet: Install-Package IronPdf
using IronPdf;

var pdf1 = PdfDocument.FromFile("document1.pdf");
var pdf2 = PdfDocument.FromFile("document2.pdf");

var merged = PdfDocument.Merge(pdf1, pdf2);
merged.SaveAs("merged.pdf");
// NuGet: Install-Package IronPdf
using IronPdf;

var pdf1 = PdfDocument.FromFile("document1.pdf");
var pdf2 = PdfDocument.FromFile("document2.pdf");

var merged = PdfDocument.Merge(pdf1, pdf2);
merged.SaveAs("merged.pdf");
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The PdfDocument.Merge() method accepts multiple documents and returns a combined result. No page iteration, no manual document model construction, no stream management—the operation completes in four lines of code.

Critical Technical Limitations

Telerik Document Processing Issues

IssueImpactIronPDF Solution
CSS parsing limitationsModern CSS frameworks like Bootstrap failFull Chromium CSS support
Div-to-paragraph conversionHTML structure flattened, layouts breakDirect HTML rendering
Flow document modelForces intermediate conversionNative HTML-to-PDF
External CSS issuesComplex selectors ignoredFull CSS file support
Memory issuesOutOfMemoryException on large docsEfficient streaming

Performance Considerations

There are reported instances of memory limitations with Telerik Document Processing, particularly with large files where the library throws OutOfMemoryException errors. IronPDF is designed to handle large documents without running into memory problems, making it a reliable choice for high-volume document production.

API Complexity Comparison

Telerik's Complex Architecture

Telerik requires understanding multiple concepts and classes:

// Telerik - Complex provider/model architecture

// 1. Import HTML to Flow Document
HtmlFormatProvider htmlProvider = new HtmlFormatProvider();
RadFlowDocument document = htmlProvider.Import(htmlContent);

// 2. Manually modify document model
RadFlowDocumentEditor editor = new RadFlowDocumentEditor(document);
Section section = document.Sections.First();
Paragraph para = section.Blocks.AddParagraph();
para.Inlines.AddText("Additional text");

// 3. Configure export settings
PdfExportSettings exportSettings = new PdfExportSettings();
exportSettings.ImageQuality = ImageQuality.High;

// 4. Create PDF provider with settings
PdfFormatProvider pdfProvider = new PdfFormatProvider();
pdfProvider.ExportSettings = exportSettings;

// 5. Export to bytes
byte[] pdfBytes = pdfProvider.Export(document);

// 6. Save to file
File.WriteAllBytes("output.pdf", pdfBytes);
// Telerik - Complex provider/model architecture

// 1. Import HTML to Flow Document
HtmlFormatProvider htmlProvider = new HtmlFormatProvider();
RadFlowDocument document = htmlProvider.Import(htmlContent);

// 2. Manually modify document model
RadFlowDocumentEditor editor = new RadFlowDocumentEditor(document);
Section section = document.Sections.First();
Paragraph para = section.Blocks.AddParagraph();
para.Inlines.AddText("Additional text");

// 3. Configure export settings
PdfExportSettings exportSettings = new PdfExportSettings();
exportSettings.ImageQuality = ImageQuality.High;

// 4. Create PDF provider with settings
PdfFormatProvider pdfProvider = new PdfFormatProvider();
pdfProvider.ExportSettings = exportSettings;

// 5. Export to bytes
byte[] pdfBytes = pdfProvider.Export(document);

// 6. Save to file
File.WriteAllBytes("output.pdf", pdfBytes);
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IronPDF's Simple Approach

// IronPDF - Direct rendering, no intermediate models

var renderer = new ChromePdfRenderer();
renderer.RenderingOptions.PaperSize = PdfPaperSize.A4;

var pdf = renderer.RenderHtmlAsPdf(htmlContent);
pdf.SaveAs("output.pdf");

// That's it - 3 lines vs 15+ lines!
// IronPDF - Direct rendering, no intermediate models

var renderer = new ChromePdfRenderer();
renderer.RenderingOptions.PaperSize = PdfPaperSize.A4;

var pdf = renderer.RenderHtmlAsPdf(htmlContent);
pdf.SaveAs("output.pdf");

// That's it - 3 lines vs 15+ lines!
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When Teams Consider Telerik Document Processing Migration

Several factors prompt development teams to evaluate alternatives to Telerik Document Processing:

CSS rendering limitations prevent modern web layouts from rendering correctly. Flexbox, CSS Grid, and Bootstrap column systems fail because the Flow Document model flattens HTML structure into sequential paragraphs.

JavaScript support absence makes it impossible to render dynamic content, SPAs, or pages that depend on client-side rendering.

Memory issues with large documents cause OutOfMemoryException errors during processing of substantial PDF files, limiting scalability for high-volume document production.

DevCraft bundle requirement may not align with teams that only need PDF functionality. The comprehensive suite includes many components that may be unnecessary for focused PDF generation requirements.

Complex API architecture with multiple format providers, document models, and explicit stream management increases development time and maintenance overhead compared to simpler alternatives.

Strengths and Trade-offs

Telerik Document Processing Strengths

  • Integration with Telerik DevCraft suite
  • Extensive documentation and community support
  • Multi-format support (Word, Excel, PowerPoint beyond PDFs)
  • Established enterprise presence

Telerik Document Processing Limitations

  • Limited CSS3 support (Flexbox, Grid fail)
  • Bootstrap layouts broken by div flattening
  • No JavaScript execution
  • Memory issues with large files
  • Complex API with multiple providers
  • DevCraft bundle requirement

IronPDF Strengths

  • Full CSS3 support including Flexbox and Grid
  • Bootstrap 5 compatibility
  • JavaScript execution
  • Native URL-to-PDF conversion
  • Stable performance with large files
  • Simple, single-class API
  • Standalone licensing

Conclusion

Telerik Document Processing and IronPDF serve different architectural preferences and technical requirements. Telerik Document Processing provides value for organizations deeply embedded in the Telerik DevCraft ecosystem requiring broad document format handling across Word, Excel, and PowerPoint beyond PDFs.

For developers seeking robust HTML-to-PDF conversion with full modern web standards support, IronPDF provides the CSS3, Flexbox, Grid, and JavaScript capabilities that Telerik's Flow Document model cannot deliver. The ability to render Bootstrap layouts correctly, handle large files efficiently, and convert URLs directly to PDF addresses common requirements that Telerik Document Processing struggles with.

When evaluating Telerik Document Processing migration to IronPDF, teams should consider their specific requirements around CSS rendering fidelity, JavaScript execution, memory performance, and API simplicity. For teams targeting .NET 10 and C# 14 in 2026 with modern web-based document generation workflows, IronPDF's Chromium-based approach provides capabilities that align with contemporary web development practices.

For implementation guidance, explore the IronPDF HTML-to-PDF tutorial and documentation covering PDF generation patterns for modern .NET applications.