Converting Word to PDF Without Office on Linux

Converting Word documents to PDF is one of the most requested features in document automation. Traditionally it often meant a Windows machine with Microsoft Office or a LibreOffice sidecar. OfficeIMO.Word.Pdf provides an in-process conversion path that can be hosted on Linux, macOS, and Windows, provided you validate fonts and runtime packaging for your deployment.

Installation

dotnet add package OfficeIMO.Word.Pdf

The package depends on OfficeIMO.Word together with QuestPDF and SkiaSharp. You still do not need Microsoft Office or LibreOffice, but on Linux containers you should provision fonts so text measurement and output quality stay predictable.

Basic Conversion

using OfficeIMO.Word;
using OfficeIMO.Word.Pdf;

// Create or open a Word document
using var doc = WordDocument.Create("Invoice.docx");
doc.AddParagraph("Invoice #10042").Bold = true;
doc.AddParagraph("Date: 2025-09-10");
doc.AddParagraph("Amount Due: $1,250.00");
doc.Save();

// Export the document directly to PDF
doc.SaveAsPdf("Invoice.pdf");

That is it. Two lines to go from DOCX to PDF once the document exists.

Stream-Based Conversion

For web applications and cloud functions, you often work with streams rather than files:

using System.IO;
using OfficeIMO.Word;
using OfficeIMO.Word.Pdf;

using var doc = WordDocument.Create("Invoice.docx");
doc.AddParagraph("Invoice #10042");
doc.Save();

using var docxStream = new MemoryStream();
doc.Save(docxStream);
docxStream.Position = 0;

using var loaded = WordDocument.Load(docxStream);
using var pdfStream = new MemoryStream();
loaded.SaveAsPdf(pdfStream);

// Upload pdfStream to blob storage or return as HTTP response

Running in Docker

Here is a minimal Dockerfile for a PDF conversion microservice:

FROM mcr.microsoft.com/dotnet/sdk:8.0-alpine AS build
WORKDIR /src
COPY . .
RUN dotnet publish -c Release -o /app

FROM mcr.microsoft.com/dotnet/aspnet:8.0-alpine
WORKDIR /app
COPY --from=build /app .

# Install font packages for decent PDF rendering
RUN apk add --no-cache icu-libs fontconfig ttf-liberation

ENTRYPOINT ["dotnet", "PdfService.dll"]

The key detail is the font packages. PDF rendering needs real font files to compute glyph widths and embed subsets. The ttf-liberation package provides metrically compatible substitutes for Times New Roman, Arial, and Courier New.

ASP.NET Core Endpoint

A minimal API endpoint that accepts a DOCX upload and returns a PDF:

using OfficeIMO.Word;
using OfficeIMO.Word.Pdf;

app.MapPost("/convert", async (IFormFile file) =>
{
    await using var input = new MemoryStream();
    await file.CopyToAsync(input);
    input.Position = 0;

    using var document = WordDocument.Load(input);
    var output = new MemoryStream();
    document.SaveAsPdf(output);
    output.Position = 0;

    return Results.File(output, "application/pdf", "converted.pdf");
});

Deploy this behind a load balancer and you have a scalable, stateless conversion service.

Font Handling Tips

• Embed fonts in the DOCX when possible. That reduces surprises, but host fonts still matter for fallback and for documents that reference fonts that are not embedded.
• Fallback fonts. If a font is missing and not embedded, the converter substitutes the closest available font. Install ttf-liberation or ttf-dejavu to minimise mismatches.
• CJK text. For Chinese, Japanese, or Korean content, install font-noto-cjk on Alpine or fonts-noto-cjk on Debian.

Limitations

The conversion engine handles paragraphs, tables, images, headers, footers, page breaks, and basic styles well. Complex features like SmartArt, embedded OLE objects, and advanced text effects may render with reduced fidelity. For those edge cases, consider Aspose or a LibreOffice sidecar container.

For many business documents, including invoices, letters, reports, and contracts, OfficeIMO.Word.Pdf can produce solid PDF output without Office automation. As always with document rendering, validate the result against the templates and fidelity requirements that matter to your workflow.

Continue with

• OfficeIMO.Word if you want to generate the source DOCX files in the same pipeline.
• Word documentation for document structure, tables, headers, and layout primitives.
• Platform support for runtime and deployment guidance across packages.
• Downloads to explore the wider package family around Word and converters.