Accessible PDF/UA from HTML in C# (tagged PDF)

Build it step by step.

1. 1Install the NuGet packages

   SelectPdf.Universal is the library. The native package carries the Chromium engine for one platform: add the one for the platform you run on.

   Windows x64 Linux x64 Linux ARM64 macOS · Apple Silicon
   terminal COPY

   dotnet add package SelectPdf.Universal
   dotnet add package SelectPdf.Universal.Native.win-x64

   terminal COPY

   dotnet add package SelectPdf.Universal
   dotnet add package SelectPdf.Universal.Native.linux-x64

   terminal COPY

   dotnet add package SelectPdf.Universal
   dotnet add package SelectPdf.Universal.Native.linux-arm64

   terminal COPY

   dotnet add package SelectPdf.Universal
   dotnet add package SelectPdf.Universal.Native.osx-arm64

2. 2Create a console app

   Any .NET 8 or .NET 10 project works. To follow along, create a console app, run the install commands above inside its folder, then replace Program.cs with the code below.

   terminal COPY

   dotnet new console -n PdfSample
   cd PdfSample

3. 3Write accessible HTML

   Program.cs · lines 3–21 COPY

   // HTML written for accessibility: a language, headings in order, alt text, a real table
   string html = """
       <html lang="en">
       <head><title>Quarterly report</title></head>
       <body>
         <h1>Quarterly report</h1>
         <p>Revenue grew in every region this quarter.</p>
         <img src="https://selectpdf.com/img/selectpdf-logo-h128.png" alt="SelectPdf logo" height="40">
         <h2>Revenue by region</h2>
         <table>
           <thead><tr><th scope="col">Region</th><th scope="col">Revenue</th></tr></thead>
           <tbody>
             <tr><td>Europe</td><td>1,200,000</td></tr>
             <tr><td>Americas</td><td>900,000</td></tr>
           </tbody>
         </table>
       </body>
       </html>
       """;

   The PDF's structure tree is built from the HTML, so the HTML decides how accessible the PDF is: lang on the html element, a title, headings in order (h1, then h2), alt text on the image, and a table with thead and th scope="col" header cells.

4. 4Declare PDF/UA-1

   Program.cs · lines 23–26 COPY

   HtmlToPdf converter = new HtmlToPdf();
   
   // declare PDF/UA-1: tags the document and writes the PDF/UA identifier
   converter.Options.AccessibilityStandard = PdfUAStandard.UA1;

   AccessibilityStandard = PdfUAStandard.UA1 tags the document and writes the PDF/UA identifier. A document that is only tagged (Options.Tagged) is accessible to a screen reader but makes no formal claim; a compliance requirement usually means the declared standard.

5. 5Set the title and language

   Program.cs · lines 28–30 COPY

   // PDF/UA requires a document title and a language
   converter.Options.Title = "Quarterly report";
   converter.Options.Language = "en-US";

   PDF/UA requires both: Title is shown instead of the file name, and Language tells a screen reader how to pronounce the text.

6. 6Convert and save

   Program.cs · lines 32–34 COPY

   PdfDocument doc = converter.ConvertHtmlString(html);
   doc.Save("report-ua1.pdf");
   doc.Close();

   ConvertHtmlString takes the structure from the rendering engine's accessible output: headings, paragraphs, the figure with its alternate text, the table and its header cells, in reading order.

7. 7Run it

   terminal COPY

   dotnet run

   The program writes report-ua1.pdf to the working folder. Without a license key, every page carries a trial watermark; set GlobalProperties.LicenseKey before the first conversion to remove it.

The complete Program.cs.

This is the exact file our samples pipeline compiled and ran on Linux ARM64 and Linux x64 and macOS ARM64 and Windows x64 to produce the output on this page.

using SelectPdf.Universal;

// HTML written for accessibility: a language, headings in order, alt text, a real table
string html = """
    <html lang="en">
    <head><title>Quarterly report</title></head>
    <body>
      <h1>Quarterly report</h1>
      <p>Revenue grew in every region this quarter.</p>
      <img src="https://selectpdf.com/img/selectpdf-logo-h128.png" alt="SelectPdf logo" height="40">
      <h2>Revenue by region</h2>
      <table>
        <thead><tr><th scope="col">Region</th><th scope="col">Revenue</th></tr></thead>
        <tbody>
          <tr><td>Europe</td><td>1,200,000</td></tr>
          <tr><td>Americas</td><td>900,000</td></tr>
        </tbody>
      </table>
    </body>
    </html>
    """;

HtmlToPdf converter = new HtmlToPdf();

// declare PDF/UA-1: tags the document and writes the PDF/UA identifier
converter.Options.AccessibilityStandard = PdfUAStandard.UA1;

// PDF/UA requires a document title and a language
converter.Options.Title = "Quarterly report";
converter.Options.Language = "en-US";

PdfDocument doc = converter.ConvertHtmlString(html);
doc.Save("report-ua1.pdf");
doc.Close();

Open the project on GitHub → this program and the variations below, ready to dotnet run

The PDF it produces.

Variations you will need next.

Each variation is a separate file in the same project, compiled and run with the program above.

PDF/UA-2 and PDF/A-4 in one file

PdfUAStandard.UA2 is the newer standard (ISO 14289-2), defined on PDF 2.0. For a document that is both accessible and archival, combine it with PdfStandard.PdfA4: PDF/A-4 is the archival level built on PDF 2.0, so it is the one that goes with PDF/UA-2.

using SelectPdf.Universal;

static class PdfUA2
{
    public static void Run()
    {
        string html = """
            <html lang="en">
            <head><title>Annual report</title></head>
            <body>
              <h1>Annual report</h1>
              <p>Accessible and archived: PDF/UA-2 and PDF/A-4 in one file.</p>
            </body>
            </html>
            """;

        HtmlToPdf converter = new HtmlToPdf();

        // PDF/UA-2 is defined on PDF 2.0, so the only archival level it combines with is PDF/A-4
        converter.Options.AccessibilityStandard = PdfUAStandard.UA2;
        converter.Options.PdfStandard = PdfStandard.PdfA4;
        converter.Options.Title = "Annual report";
        converter.Options.Language = "en-US";

        PdfDocument doc = converter.ConvertHtmlString(html);
        doc.Save("report-ua2-pdfa4.pdf");
        doc.Close();
    }
}

An archived, accessible invoice (PDF/A-3A and PDF/UA-1)

Archiving and accessibility are separate standards, so PdfStandard and AccessibilityStandard combine. PDF/A-3A is the accessible level of PDF/A-3, and pairs with PDF/UA-1.

using SelectPdf.Universal;

static class ArchivedInvoice
{
    public static void Run()
    {
        string html = """
            <html lang="en">
            <head><title>Invoice 2026-0042</title></head>
            <body>
              <h1>Invoice 2026-0042</h1>
              <p>Billed to Contoso Ltd.</p>
            </body>
            </html>
            """;

        HtmlToPdf converter = new HtmlToPdf();

        // PDF/A-3A (archival, level A = accessible) together with PDF/UA-1
        converter.Options.PdfStandard = PdfStandard.PdfA3A;
        converter.Options.AccessibilityStandard = PdfUAStandard.UA1;
        converter.Options.Title = "Invoice 2026-0042";
        converter.Options.Language = "en-US";

        PdfDocument doc = converter.ConvertHtmlString(html);
        doc.Save("invoice-pdfa3a-ua1.pdf");
        doc.Close();
    }
}

Common problems and fixes.

Good to know.

• AccessibilityStandard declares PDF/UA-1 or PDF/UA-2: it turns tagging on and writes the PDF/UA identifier that validators and assistive software look for. Source
• Both standards require a document title and a language. Source
• PDF/UA-2 is written as a PDF 2.0 document; internal links and outline entries also carry a structure destination, so a reader lands at the right place in the reading order. Source
• The structure comes from the HTML: images need alt text, headings should be in order, and tables need real table markup. Source
• Tagged PDF is part of the commercial library; it is not in the free Community Edition. Source