The Best Free and Open-Source PDF Tools
For most people: SumatraPDF (Windows) or Okular to read, PDFsam Basic to merge and split, Xournal++ to annotate and sign, and Stirling-PDF for an all-in-one toolbox. For power users, the free command-line tools qpdf, Ghostscript and OCRmyPDF handle repair, compression and OCR. All are open source, with no watermarks or subscriptions.
Every tool on this page is open source: the code is public, it costs nothing, and there are no watermarks, page limits or subscriptions. We’ve grouped them by what you want to do.
Download only from the official website or app store listed for each project. Unofficial “free PDF editor” downloads are a common way to spread adware.
Quick picks
| I want to… | Windows | Mac | Linux |
|---|---|---|---|
| Read PDFs | SumatraPDF, Okular | Preview (built in), Sioyek | Okular, Sioyek |
| Merge, split, rotate | PDFsam Basic | PDFsam Basic | PDFsam Basic, PDF Arranger |
| Annotate, draw, sign | Xournal++ | Xournal++ | Xournal++, Okular |
| Change existing text | LibreOffice Draw | LibreOffice Draw | LibreOffice Draw |
| Do everything in one place | Stirling-PDF | Stirling-PDF | Stirling-PDF |
| OCR scans, compress, repair | OCRmyPDF, qpdf, Ghostscript (command line) | same | same |
PDF readers
SumatraPDF (Windows)
A tiny, very fast reader that opens instantly, even for huge files. It also reads EPUB, MOBI and comic book files. There’s no editing: it’s purely for reading and printing, which is exactly why it’s so light. License: GPL-3.0.
Okular (Windows, Linux)
KDE’s document viewer. Beyond reading, it can highlight, add notes, fill forms and add a signature, which makes it a solid everyday reader and light annotator. License: GPL.
Sioyek (Windows, Mac, Linux)
Designed for research papers and technical books: it previews references and figures when you hover over them and keeps track of where you left off. License: GPL-3.0.
Don’t forget your browser: Chrome, Edge, Firefox and Safari all open PDFs, and Edge can add text, highlights and drawings. On a Mac, the built-in Preview app also merges, signs and annotates.
Merge, split and reorganise
PDFsam Basic (Windows, Mac, Linux)
The go-to free tool for merging, splitting, rotating and extracting pages. It can split by page ranges, bookmarks or file size, and it works entirely offline. The free edition is “Basic”; the paid “Enhanced” and “Visual” editions are separate products, so you don’t need them for these tasks.
PDF Arranger (Linux, Windows)
A simple visual editor: see every page as a thumbnail, then drag to reorder, rotate, crop, delete or combine pages from several files. License: GPL-3.0.
Step-by-step: How to merge PDF files · How to split a PDF
Annotate, fill and sign
Xournal++ (Windows, Mac, Linux)
Open a PDF and write, draw, highlight, add text or a signature, then export a new PDF. It’s especially good with a stylus or drawing tablet, so it’s popular for marking up lecture slides and signing documents. License: GPL.
See also: How to sign a PDF · How to fill out a PDF form
Edit existing text
LibreOffice Draw (Windows, Mac, Linux)
Part of the free LibreOffice suite. It opens PDFs with each line as an editable text box, so you can fix typos, change numbers and move elements, then export back to PDF. Fonts not installed on your computer are substituted, so check the result. License: MPL-2.0.
Full walkthrough: How to change text in a PDF
All-in-one toolboxes
Stirling-PDF (desktop app, browser or self-hosted)
The most complete open-source PDF toolbox: 50+ tools for merging, splitting, converting, compressing, OCR, signing, redacting, watermarking and more. You can run it as a desktop app, or host it on your own computer or server with one Docker command, so files never leave your machine:
docker run -p 8080:8080 docker.stirlingpdf.com/stirlingtools/stirling-pdfThen open http://localhost:8080 in your browser. License: the core is MIT; some newer enterprise features are under a separate proprietary licence.
BentoPDF (browser, self-hostable)
A privacy-focused toolkit that runs entirely in your browser: merging, splitting, editing and converting happen on your device, without uploading files. You can also host your own copy. License: AGPL-3.0.
Command-line power tools
These have no graphical interface, but they are the engines behind many PDF apps and are unbeatable for batch jobs.
| Tool | Best for | Example | License |
|---|---|---|---|
| OCRmyPDF | Making scanned PDFs searchable | ocrmypdf scan.pdf searchable.pdf |
MPL-2.0 |
| qpdf | Repairing damaged files, removing a known password, merging | qpdf --decrypt --password=secret in.pdf out.pdf |
Apache-2.0 |
| Ghostscript | Compressing PDFs, converting to PDF/A | gs -sDEVICE=pdfwrite -dPDFSETTINGS=/ebook -o small.pdf in.pdf |
AGPL-3.0 |
| pdfcpu | Merging, splitting, watermarking, encrypting, validating | pdfcpu merge out.pdf a.pdf b.pdf |
Apache-2.0 |
| Poppler utils | Extracting text and images, splitting | pdftotext in.pdf out.txt |
GPL |
On Mac, install them with Homebrew (brew install ocrmypdf qpdf ghostscript); on Linux, use your package manager.
Guides: Make a scanned PDF searchable · How to compress a PDF
Check PDF/A compliance
veraPDF (Windows, Mac, Linux)
The reference open-source validator for PDF/A (archiving) and PDF/UA (accessibility). Use it when a court, university or government portal rejects your file as “not valid PDF/A”. Learn more in PDF versions and PDF/A.
For developers
Building PDF features into your own software? See our Python PDF libraries comparison and AI tools for parsing PDFs.
Frequently asked questions
Is there a completely free alternative to Adobe Acrobat?
No single free app matches Acrobat Pro feature for feature, but a combination comes close: Stirling-PDF for most operations, LibreOffice Draw for editing text, Xournal++ for annotating and signing, and OCRmyPDF for OCR. For simply reading PDFs, any web browser or SumatraPDF is enough.
What's the difference between free and open-source software?
Free software costs nothing but may still show ads, add watermarks, limit features or collect data. Open-source software publishes its source code, so anyone can check what it does. It is almost always free, without watermarks or artificial limits.
Are online PDF tools safe?
Reputable services delete files after a few hours, but your document is still uploaded to someone else's server. For contracts, IDs and financial or medical records, use desktop software, or browser-based tools that process files locally.
Which free PDF editor can change existing text?
LibreOffice Draw is the best free option. It opens PDFs with every line as an editable text box. See our guide on how to change text in a PDF.
Was this page helpful?
Thanks for the feedback!