Best Open-Source PDF Converters 2026: 6 Options Compared

PDF conversion is really several jobs, and open-source tools are good at different ones. Turning Word, Excel and PowerPoint files into PDF is a job for LibreOffice or, if you need it as a web service inside your own system, Gotenberg, a Docker API that converts documents to PDF. Converting Markdown, HTML and similar markup into other formats, including PDF output, is what Pandoc does best. Calibre converts between e-book formats and handles PDF as part of that work. Stirling PDF packs conversion, editing, merging and OCR into one interface and runs in a browser, on the desktop or on your own server. OCRmyPDF is the right tool when the PDF is a scan and you want searchable text rather than a new file format. Pick LibreOffice for occasional desktop conversions, Gotenberg for software that must generate PDFs automatically, and Pandoc if your content starts as Markdown. Output quality depends on the source: fonts, complex tables and layouts may shift between formats, so check a sample before you convert in bulk. Conversion from a PDF back to an editable Word file is the hardest direction for every tool listed. Licences below are from each project's pages as of the check date.

LibreOffice

MPL-2.0 desktop suite that exports documents, sheets and slides to PDF with no account. Reliable for office files; PDF import is limited.

Price: Free (download and use at no cost per its site) (LibreOffice pricing, checked 2026-10-22).

Platforms and license: Windows, macOS, Linux. MPL-2.0 (open source) (license source).

Best for: Office files to PDF.

Worth knowing: Desktop suite of Writer, Calc, Impress, Draw, Base and Math; it has no built-in cloud storage or email.

Stirling PDF

MIT with some directories under separate licences. Free plan covers web, desktop and self-hosted use of 60+ tools, with 1,000 monthly credits.

Price: Free (Free plan at $0 with no card: web, desktop and self-hosted use, 60+ PDF tools and 1,000 monthly credits); paid from $99 per month (Team, 100 users) (Stirling PDF pricing, checked 2026-10-23).

Platforms and license: Web browser, Desktop app, Self-hosted (Docker). MIT, with some directories under separate licenses (open source) (license source).

Project activity: 95.2k GitHub stars · latest release v3.2.2 (Oct 24, 2026) · last commit Oct 27, 2026

Best for: One interface for many PDF tasks.

Worth knowing: LICENSE file says MIT except app/proprietary and other directories with their own licenses. Repository README lists edit, merge, split, sign, redact, convert, OCR and compress.

Pandoc

GPL-2.0 command-line converter for markup formats, including writing PDF output. It does not read PDFs as input.

Price: Free (Free and open source markup converter) (Pandoc pricing, checked 2026-10-24).

Platforms and license: Command line. GPL-2.0 (open source) (license source).

Project activity: 46.7k GitHub stars · latest release 3.13 (Oct 26, 2026) · last commit Oct 27, 2026

Best for: Markdown and HTML to PDF.

Worth knowing: GitHub describes it as a universal markup converter. License taken from the repository metadata and LICENSE file; description from the project README. No paid plan was checked.

Gotenberg

MIT Docker API for converting documents to PDF, meant to be called from your own software. No graphical interface.

Price: Free (Free and open source Docker-based API) (Gotenberg pricing, checked 2026-10-24).

Platforms and license: Docker (HTTP API). MIT (open source) (license source).

Project activity: 13.5k GitHub stars · latest release v8.39.0 (Oct 27, 2026) · last commit Oct 27, 2026

Best for: Developers automating PDF output.

Worth knowing: README: a Docker-based API for converting documents to PDF. License taken from the repository metadata and LICENSE file; description from the project README. No paid plan was checked.

calibre

GPL-3.0 e-book manager and converter. Useful if your PDF starts or ends as an EPUB or MOBI file; PDF handling was not tested here.

Price: Free (Free and open source e-book manager and converter) (calibre pricing, checked 2026-10-24).

Platforms and license: Desktop. GPL-3.0 (open source) (license source).

Project activity: 26.3k GitHub stars · latest release v9.17.0 (Oct 23, 2026) · last commit Oct 27, 2026

Best for: E-book format conversion.

Worth knowing: Whether a given PDF converts cleanly was not tested. License taken from the repository metadata and LICENSE file; description from the project README. No paid plan was checked.

OCRmyPDF

MPL-2.0 tool that adds a text layer to scanned PDFs rather than changing format. Command-line only.

Price: Free (Free; adds a searchable text layer to scanned PDFs, needs Tesseract and Ghostscript installed) (OCRmyPDF pricing, checked 2026-10-24).

Platforms and license: Linux, Windows, macOS, FreeBSD. MPL-2.0 (open source) (license source).

Project activity: 35.2k GitHub stars · latest release v17.13.0 (Sep 28, 2026) · last commit Oct 25, 2026

Best for: Making scans searchable.

Worth knowing: Scriptable command-line tool; Docker images for x64 and ARM.

Which one to pick

• You convert a few Word files to PDF on a laptop: LibreOffice
• Your app must generate PDFs from HTML or Office files on a server: Gotenberg
• You write in Markdown and want a PDF at the end: Pandoc
• You want merge, convert and OCR under one roof: Stirling PDF