A Comparison between IronPDF and PDFium.NET

1.1. Using Visual Studio

In your Visual Studio project, from the "Tools" Menu or right-click your project in the Solution Explorer and select "Manage NuGet Packages". Both these options are shown below in the screenshots.

Once the NuGet Package Manager is opened, browse for the IronPDF package and install it, as shown in the screenshot below.

1.2. Using the Developer Command Prompt

IronPDF can also be downloaded through the Developer Command Prompt. Follow the steps below:

• Open the Developer Command Prompt or Package Manager Console from the Tools menu.
• Type the following command:

Install-Package IronPdf

• Press the Enter Key
• This will download and install the library

1.3. Download the NuGet Package Directly

IronPDF can also be directly downloaded by visiting the NuGet IronPDF Package. The steps are:

• Look for Download Package and click on it.
• The package will be downloaded and installed.

1.4. Install IronPDF by Downloading the library

You can also download the IronPDF.DLL file directly from IronPDF's package page.

Reference the IronPDF library in your project by using the following steps:

• Right-click the Solution in the Solution Explorer and Select References
• Browse for the IronPDF.dll library
• Click OK!

All done! IronPDF is downloaded and installed. We will now work on installing the PDFium.NET SDK library.

3.1. Using IronPDF

IronPDF provides multiple methods for generating PDF files. Let's have a look at two important ones.

Existing URL to PDF

IronPDF converts existing URLs directly to PDF using its built-in Chromium rendering engine.

Consider the following source code.

IronPdf.ChromePdfRenderer Renderer = new IronPdf.ChromePdfRenderer();

// Use RenderUrlAsPdf method to convert a given URL to a PDF document
using var Pdf = Renderer.RenderUrlAsPdf("https://ironpdf.com/");

// Save the generated PDF document
Pdf.SaveAs("url.pdf");

IronPdf.ChromePdfRenderer Renderer = new IronPdf.ChromePdfRenderer();

// Use RenderUrlAsPdf method to convert a given URL to a PDF document
using var Pdf = Renderer.RenderUrlAsPdf("https://ironpdf.com/");

// Save the generated PDF document
Pdf.SaveAs("url.pdf");

$vbLabelText   $csharpLabel

HTML Input String to PDF

The following code snippet shows how an HTML string can be used to render a PDF page. You can use simple HTML, or combine it with CSS, images, and JavaScript content that executes before conversion.

var Renderer = new IronPDF.ChromePdfRenderer();

// Render HTML as a PDF
using var PDF = Renderer.RenderHtmlAsPdf("<h1>Html with CSS and Images</h1>");
PDF.SaveAs("pixel-perfect.pdf");

// Load external HTML assets: images, css, and javascript
// An optional BasePath 'C:\site\assets\' is set as the file location to load assets from
using var AdvancedPDF = Renderer.RenderHtmlAsPdf("<img src='logo_square.png'>", @"e:\site\assets\");
AdvancedPDF.SaveAs("html-with-assets.pdf");

var Renderer = new IronPDF.ChromePdfRenderer();

// Render HTML as a PDF
using var PDF = Renderer.RenderHtmlAsPdf("<h1>Html with CSS and Images</h1>");
PDF.SaveAs("pixel-perfect.pdf");

// Load external HTML assets: images, css, and javascript
// An optional BasePath 'C:\site\assets\' is set as the file location to load assets from
using var AdvancedPDF = Renderer.RenderHtmlAsPdf("<img src='logo_square.png'>", @"e:\site\assets\");
AdvancedPDF.SaveAs("html-with-assets.pdf");

$vbLabelText   $csharpLabel

The output is as follows:

3.2. Using PDFium.NET

PDFium.NET generates PDF documents on the fly using images and text objects. Its rendering pipeline is built around low-level page composition rather than HTML-based conversion, so URL and HTML string-to-PDF workflows are outside its current scope.

Below is an example code for generating PDFs using building PDFium.NET:

public void CreatePDF()
{
    // Step 1: Initialize PDF library and create an empty document
    PdfCommon.Initialize();
    var doc = PdfDocument.CreateNew();  // Create a new PDF document

    // Step 2: Add a new page
    // Arguments: page width: 8.27", page height: 11.69", Unit of measure: inches
    //  The PDF unit of measure is a point. There are 72 points in one inch.
    var page = doc.Pages.InsertPageAt(doc.Pages.Count, 8.27f * 72, 11.69f * 72);

    // Step 3: Add graphics and text contents to the page
    // Insert image from file using the standard System.Drawing.Bitmap class
    using (PdfBitmap logo = PdfBitmap.FromFile(@"e:\site\assets\logo_square.png"))
    {
        PdfImageObject imageObject = PdfImageObject.Create(doc, logo, 0, 0);
        // Set image resolution to 300 DPI and location to 1.69 x 10.0 inches
        imageObject.Matrix = new FS_MATRIX(logo.Width * 72 / 300, 0, 0, logo.Height * 72 / 300, 1.69 * 72, 10.0 * 72);
        page.PageObjects.Add(imageObject);
    }

    // Create fonts for text objects
    PdfFont calibryBold = PdfFont.CreateFont(doc, "CalibriBold");
    // Insert text objects at 7.69"; 11.02" and font size is 25
    PdfTextObject textObject = PdfTextObject.Create("Sample text", 7.69f * 72, 11.02f * 72, calibryBold, 25);
    textObject.FillColor = FS_COLOR.Black;
    page.PageObjects.Add(textObject);

    // Step 5: Generate page content and save PDF file
    // Argument: PDF file name
    page.GenerateContent();
    doc.Save(@"e:\site\sample_document.pdf", SaveFlags.NoIncremental);
}

public void CreatePDF()
{
    // Step 1: Initialize PDF library and create an empty document
    PdfCommon.Initialize();
    var doc = PdfDocument.CreateNew();  // Create a new PDF document

    // Step 2: Add a new page
    // Arguments: page width: 8.27", page height: 11.69", Unit of measure: inches
    //  The PDF unit of measure is a point. There are 72 points in one inch.
    var page = doc.Pages.InsertPageAt(doc.Pages.Count, 8.27f * 72, 11.69f * 72);

    // Step 3: Add graphics and text contents to the page
    // Insert image from file using the standard System.Drawing.Bitmap class
    using (PdfBitmap logo = PdfBitmap.FromFile(@"e:\site\assets\logo_square.png"))
    {
        PdfImageObject imageObject = PdfImageObject.Create(doc, logo, 0, 0);
        // Set image resolution to 300 DPI and location to 1.69 x 10.0 inches
        imageObject.Matrix = new FS_MATRIX(logo.Width * 72 / 300, 0, 0, logo.Height * 72 / 300, 1.69 * 72, 10.0 * 72);
        page.PageObjects.Add(imageObject);
    }

    // Create fonts for text objects
    PdfFont calibryBold = PdfFont.CreateFont(doc, "CalibriBold");
    // Insert text objects at 7.69"; 11.02" and font size is 25
    PdfTextObject textObject = PdfTextObject.Create("Sample text", 7.69f * 72, 11.02f * 72, calibryBold, 25);
    textObject.FillColor = FS_COLOR.Black;
    page.PageObjects.Add(textObject);

    // Step 5: Generate page content and save PDF file
    // Argument: PDF file name
    page.GenerateContent();
    doc.Save(@"e:\site\sample_document.pdf", SaveFlags.NoIncremental);
}

The output is as follows:

Comparing the two outputs, IronPDF's HTML rendering approach handles image placement automatically -- no manual scaling is required, and you can also convert standalone images directly into PDF documents when needed. PDFium.NET produces a similar result, though it relies on explicit image-scaling code to position content correctly. If we skip the following line in the code:

imageObject.Matrix = new FS_MATRIX(logo.Width * 72 / 300, 0, 0, logo.Height * 72 / 300, 1.69 * 72, 10.0 * 72);

imageObject.Matrix = new FS_MATRIX(logo.Width * 72 / 300, 0, 0, logo.Height * 72 / 300, 1.69 * 72, 10.0 * 72);

The output will be:

4.1. Using IronPDF

Merging two or more PDFs is easy in IronPDF. Using the Merge method, you can combine two or more PDFs where each file is separated by a comma. The code is as follows:

using IronPdf;

var html_a = @"<p> [PDF_A] </p>
                <p> [PDF_A] 1st Page </p>
                <div style = 'page-break-after: always;'></div>
                <p> [PDF_A] 2nd Page</p>";

var html_b = @"<p> [PDF_B] </p>
                <p> [PDF_B] 1st Page </p>
                <div style = 'page-break-after: always;'></div>
                <p> [PDF_B] 2nd Page</p>";

var Renderer = new IronPDF.ChromePdfRenderer();

// Render HTML documents as PDFs
var pdfdoc_a = Renderer.RenderHtmlAsPdf(html_a);
var pdfdoc_b = Renderer.RenderHtmlAsPdf(html_b);

// Merge the documents into one PDF
var merged = IronPDF.PdfDocument.Merge(pdfdoc_a, pdfdoc_b);

// Save the merged document
merged.SaveAs("Merged.PDF");

using IronPdf;

var html_a = @"<p> [PDF_A] </p>
                <p> [PDF_A] 1st Page </p>
                <div style = 'page-break-after: always;'></div>
                <p> [PDF_A] 2nd Page</p>";

var html_b = @"<p> [PDF_B] </p>
                <p> [PDF_B] 1st Page </p>
                <div style = 'page-break-after: always;'></div>
                <p> [PDF_B] 2nd Page</p>";

var Renderer = new IronPDF.ChromePdfRenderer();

// Render HTML documents as PDFs
var pdfdoc_a = Renderer.RenderHtmlAsPdf(html_a);
var pdfdoc_b = Renderer.RenderHtmlAsPdf(html_b);

// Merge the documents into one PDF
var merged = IronPDF.PdfDocument.Merge(pdfdoc_a, pdfdoc_b);

// Save the merged document
merged.SaveAs("Merged.PDF");

4.2. Using PDFium.NET

Using PDFium.NET, you can not only merge multiple PDF files into a single file, but also select specific pages from the source files and combine them into one PDF document.

The code below shows how it can be done using the ImportPages method:

public void MergePDF()
{
    // Initialize the SDK library.
    PdfCommon.Initialize();

    // Open and load a PDF document into which other files will be merged 
    using (var mainDoc = PdfDocument.Load(@"c:\test001.pdf")) // Read source PDF File #1
    {
        // Open one PDF document.
        using (var doc = PdfDocument.Load(@"c:\doc1.pdf")) // Read PDF File #2
        {
            // Import all pages from the document
            mainDoc.Pages.ImportPages(
                doc,
                string.Format("1-{0}", doc.Pages.Count),
                mainDoc.Pages.Count
                );
        }

        // Open another PDF document.
        using (var doc = PdfDocument.Load(@"c:\doc2.pdf"))
        {
            // Import all pages from the document
            mainDoc.Pages.ImportPages(
                doc,
                string.Format("1-{0}", doc.Pages.Count),
                mainDoc.Pages.Count
                );
        }

        // Save the merged document
        mainDoc.Save(@"c:\ResultDocument.pdf", SaveFlags.NoIncremental);
    }
}

public void MergePDF()
{
    // Initialize the SDK library.
    PdfCommon.Initialize();

    // Open and load a PDF document into which other files will be merged 
    using (var mainDoc = PdfDocument.Load(@"c:\test001.pdf")) // Read source PDF File #1
    {
        // Open one PDF document.
        using (var doc = PdfDocument.Load(@"c:\doc1.pdf")) // Read PDF File #2
        {
            // Import all pages from the document
            mainDoc.Pages.ImportPages(
                doc,
                string.Format("1-{0}", doc.Pages.Count),
                mainDoc.Pages.Count
                );
        }

        // Open another PDF document.
        using (var doc = PdfDocument.Load(@"c:\doc2.pdf"))
        {
            // Import all pages from the document
            mainDoc.Pages.ImportPages(
                doc,
                string.Format("1-{0}", doc.Pages.Count),
                mainDoc.Pages.Count
                );
        }

        // Save the merged document
        mainDoc.Save(@"c:\ResultDocument.pdf", SaveFlags.NoIncremental);
    }
}

5.1. Using IronPDF

One of the most important features nowadays is signing a PDF document with PFX certificates digitally. IronPDF provides this facility. The code goes as follows:

using IronPdf;

// Cryptographically sign an existing PDF in 1 line of code!
new IronPDF.Signing.PdfSignature("Iron.p12", "123456").SignPdfFile("any.pdf");

/***** Advanced example for more control *****/

// Step 1. Create a PDF
var Renderer = new IronPdf.ChromePdfRenderer();
var doc = Renderer.RenderHtmlAsPDF("<h1>Testing 2048 bit digital security</h1>");

// Step 2. Create a Signature.
// You may create a .pfx or .p12 PDF signing certificate using Adobe Acrobat Reader.

var signature = new IronPDF.Signing.PdfSignature("Iron.pfx", "123456");

// Step 3. Handwritten signature graphic
signature.LoadSignatureImageFromFile("handwriting.png");

// Step 4. Sign the PDF with the PDFSignature. Multiple signing certificates may be used
doc.SignPdfWithDigitalSignature(signature);

// Step 4. The PDF is not signed until saved to file, stream, or byte array.
doc.SaveAs("signed.pdf"); 

using IronPdf;

// Cryptographically sign an existing PDF in 1 line of code!
new IronPDF.Signing.PdfSignature("Iron.p12", "123456").SignPdfFile("any.pdf");

/***** Advanced example for more control *****/

// Step 1. Create a PDF
var Renderer = new IronPdf.ChromePdfRenderer();
var doc = Renderer.RenderHtmlAsPDF("<h1>Testing 2048 bit digital security</h1>");

// Step 2. Create a Signature.
// You may create a .pfx or .p12 PDF signing certificate using Adobe Acrobat Reader.

var signature = new IronPDF.Signing.PdfSignature("Iron.pfx", "123456");

// Step 3. Handwritten signature graphic
signature.LoadSignatureImageFromFile("handwriting.png");

// Step 4. Sign the PDF with the PDFSignature. Multiple signing certificates may be used
doc.SignPdfWithDigitalSignature(signature);

// Step 4. The PDF is not signed until saved to file, stream, or byte array.
doc.SaveAs("signed.pdf"); 

Digital signing is outside PDFium.NET's current scope, so teams requiring this capability would need to integrate an additional library or evaluate a tool like IronPDF that includes it as a first-class operation.

IronPDF Pricing and Licensing

IronPDF is free to use for developing simple applications and can be licensed for commercial use at any time. It provides single project licenses, single developer licenses, agencies, and multinational organizations licenses. It also provides SaaS and OEM redistribution licenses and support.

All IronPDF licenses are available with a 30-day money-back guarantee, plus a year of software support and upgrades. Most importantly, it is a perpetual license (one-time purchase). The Lite package is available. There are absolutely no recurring fees with IronPDF products. More detailed information about the available licenses is on the IronPDF Licensing page.

PDFium.NET Pricing and Licensing

PDFium.NET provides a perpetual license. You can use this supported SDK version with your registration key forever. However, the key only works with some specific SDK versions that depend on the date of license purchase or renewal. You can install any new product version for free, provided that it was released before or within one year of your purchase. PDFium.NET also provides 3 different license packages:

• Single Project License is designed for single developers and small teams working on one project. Starting from $720.
• Organization License is designed for development teams working on multiple projects.
• Single Developer License is designed for single developers and freelancers working for multiple clients.

You can visit the PDFium.NET Purchase page for complete pricing details.

Beyond license cost, total project cost includes the developer hours spent on coordinate-based page layout, manual image scaling, and integrating separate libraries for capabilities like digital signing and HTML-to-PDF conversion. For teams evaluating cost over a multi-year project lifecycle, these integration and maintenance hours frequently eclipse the difference between the two libraries' sticker prices.