Convert DOCX to PDF on Linux in C#

Build it step by step.

1. 1Install the NuGet packages

   SelectPdf.Universal is the library. This guide needs no native engine package, so the same install command works on every platform.

   terminal COPY

   dotnet add package SelectPdf.Universal

2. 2Create a console app

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

   terminal COPY

   dotnet new console -n PdfSample
   cd PdfSample

3. 3Import the namespace

   Program.cs · lines 1–1 COPY

   using SelectPdf.Universal;

   WordToPdf and everything it returns are in SelectPdf.Universal. Word to PDF needs only the SelectPdf.Universal package; the Native package is needed when you also convert HTML.

4. 4Create the converter

   Program.cs · lines 3–3 COPY

   WordToPdf converter = new WordToPdf();

   WordToPdf exposes Options, Header and Footer, the same way the HTML converter does.

5. 5Keep the pages of the Word document

   Program.cs · lines 5–6 COPY

   // Document (the default): every page keeps the size and orientation it has in Word
   converter.Options.PageSetup = WordPageSetup.Document;

   WordPageSetup.Document, the default, keeps every page the size and orientation the Word document gives it. WordPageSetup.Options reflows the text onto the page size, orientation and margins of the options instead (see the first variation).

6. 6Build the outline from the headings

   Program.cs · lines 8–9 COPY

   // the PDF outline is built from the document's headings
   converter.Options.Bookmarks = WordBookmarks.Headings;

   Bookmarks decides what the PDF outline is made from: the document's headings (the default, nested by level), its Word bookmarks, or nothing.

7. 7Convert the DOCX file

   Program.cs · lines 11–13 COPY

   // the format is taken from the file extension
   PdfDocument doc = converter.ConvertFile("report.docx");
   Console.WriteLine($"Pages: {converter.ConversionResult.PdfPageCount}, bookmarks: {doc.Bookmarks.Count}");

   ConvertFile takes the format from the file extension and returns a PdfDocument. ConversionResult describes the document produced, here its page count. A missing or unreadable file throws WordToPdfException.

8. 8Save the PDF

   Program.cs · lines 15–16 COPY

   doc.Save("report.pdf");
   doc.Close();

   Save writes the file and Close releases the document. Before saving, the PdfDocument can be changed like any other: stamped, merged or encrypted.

9. 9Run it

   terminal COPY

   dotnet run

   The program writes report.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;

WordToPdf converter = new WordToPdf();

// Document (the default): every page keeps the size and orientation it has in Word
converter.Options.PageSetup = WordPageSetup.Document;

// the PDF outline is built from the document's headings
converter.Options.Bookmarks = WordBookmarks.Headings;

// the format is taken from the file extension
PdfDocument doc = converter.ConvertFile("report.docx");
Console.WriteLine($"Pages: {converter.ConversionResult.PdfPageCount}, bookmarks: {doc.Bookmarks.Count}");

doc.Save("report.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.

Reflow onto A4 landscape with page numbers

WordPageSetup.Options reflows the text onto PdfPageSize, PdfPageOrientation and the margins of the options (in points, 72 to the inch), replacing the Word document's own margins. DisplayFooter and a PdfTextSection with {page_number} and {total_pages} add a page-number footer band.

using SelectPdf.Universal;

static class ReflowA4Landscape
{
    public static void Run()
    {
        WordToPdf converter = new WordToPdf();

        // Options: reflow the text onto A4 landscape with one-inch (72 pt) margins
        converter.Options.PageSetup = WordPageSetup.Options;
        converter.Options.PdfPageSize = PdfPageSize.A4;
        converter.Options.PdfPageOrientation = PdfPageOrientation.Landscape;
        converter.Options.MarginTop = 72;
        converter.Options.MarginBottom = 72;
        converter.Options.MarginLeft = 72;
        converter.Options.MarginRight = 72;

        // page numbers in a footer band
        converter.Options.DisplayFooter = true;
        converter.Footer.Height = 30;
        converter.Footer.Add(new PdfTextSection(0, 10, 500, "Page {page_number} of {total_pages}",
            PdfFont.CreateStandardFont(PdfStandardFont.Helvetica, 9), new PdfColor(80, 80, 80)));

        PdfDocument doc = converter.ConvertFile("report.docx");
        doc.Save("report-a4-landscape.pdf");
        doc.Close();
    }
}

Convert a DOCX held in memory

ConvertBytes converts a document held in a byte array, such as a file uploaded to a web app, and ConvertStream reads one from a stream. The format is detected from the content for docx, doc, rtf and WordML; plain text, html and markdown must be named with the WordFormat overload. Save() without arguments returns the PDF as a byte array.

using SelectPdf.Universal;

static class ConvertUploadedBytes
{
    public static void Run()
    {
        // a document held in memory, such as a file uploaded to a web app
        byte[] upload = File.ReadAllBytes("report.docx");

        // the format is detected from the content (docx, doc, rtf, WordML)
        WordToPdf converter = new WordToPdf();
        PdfDocument doc = converter.ConvertBytes(upload);

        // Save() without arguments returns the PDF as a byte array
        byte[] pdf = doc.Save();
        doc.Close();

        File.WriteAllBytes("report-from-bytes.pdf", pdf);
    }
}

Put a cover page in front of the converted document

The Word converter returns a PdfDocument, like the HTML converter, so the two combine with Append. The appended documents must stay open until the merged document is saved. Converting the HTML cover needs the SelectPdf.Universal.Native package for your platform, for example SelectPdf.Universal.Native.linux-x64.

using SelectPdf.Universal;

static class AddCoverPage
{
    public static void Run()
    {
        // a cover page made from HTML
        HtmlToPdf html = new HtmlToPdf();
        PdfDocument cover = html.ConvertHtmlString("""
            <div style="font-family: Arial; margin-top: 300px; text-align: center">
              <h1>Contoso Ltd</h1>
              <p>Board pack, October 2026</p>
            </div>
            """);

        // the Word document, converted straight into a PdfDocument
        PdfDocument report = new WordToPdf().ConvertFile("report.docx");

        // append both to a new document; they stay open until it is saved
        PdfDocument pack = new PdfDocument();
        pack.Append(cover);
        pack.Append(report);
        pack.Save("board-pack.pdf");

        pack.Close();
        cover.Close();
        report.Close();
    }
}

Common problems and fixes.

Good to know.

• Converting Word to PDF needs no Microsoft Word or Office: the Word engine is part of the SelectPdf.Universal library. Source
• The converter reads docx, docm, dotx, dotm, doc and dot files, plus rtf, plain text, WordML, html and markdown. Source
• A font family the host does not have is served from the bundled Liberation fonts, metric-compatible with Arial, Times New Roman and Courier New, so the same document converts in a Linux container with no fonts installed. Source
• The bundled Liberation fonts cover Latin, Greek and Cyrillic; for other scripts, install fonts on the host or reference the SelectPdf.Universal.Fonts package. Source
• The Word to PDF converter is available only in the full commercial SelectPdf library, not in the free Community Edition. Source