7 Open Source PDF Compare Tools (Free, 2026)
Not everyone wants a subscription. Whether it’s budget, principle, or privacy, open-source PDF comparison tools have a loyal following — and several are genuinely good. Here are the best free and open-source options we’ve researched, ranked by usefulness.
Quick answer: The best open-source PDF compare tool is DiffPDF v2.1.3 (GPL) — a full GUI with word, character, and appearance comparison. For command-line and Git workflows, use diff-pdf. For batch OCR pipelines, OCRmyPDF + diff covers scanned documents. Newer projects like PDFComp add modern touches like font-attribute comparison.
1. DiffPDF v2.1.3 — Best Overall (GPL)
The classic. A graphical desktop app with three comparison modes (Words, Characters, Appearance), exclusion rectangles, and page-range selection. Free forever, offline, no account. The only real downside is that development stopped — but v2.1.3 remains perfectly functional on Windows and Linux.
2. diff-pdf — Best for Developers & Git
A command-line tool that renders PDF pages to images and diffs them — scriptable, CI-friendly, and integrates with Git as a difftool (brew install diff-pdf). Note: despite the similar name, it’s an independent project, not related to DiffPDF. See our explainer.
3. PDFComp — Newcomer to Watch
A newer open-source GUI project with side-by-side viewing, synchronized page navigation, jump-to-difference, and experimental character-attribute comparison (font color, strikethrough, underline) — something even DiffPDF doesn’t do. Worth watching as it matures.
4. OCRmyPDF + diff — Best for Scanned PDFs
Not a comparison tool itself, but the missing piece: OCRmyPDF adds searchable text layers to scanned PDFs from the command line, after which any text diff (even plain diff on extracted text) works. The standard open-source pipeline for scanned-document QA. See our scanned-PDF workflow.
5. pdf-tools via Poppler — Best for Scripting Text Extraction
The Poppler utilities (pdftotext, pdfinfo) are the backbone of countless DIY comparison scripts: extract text from both PDFs, then diff the results. Crude but extremely reliable for “did the text change at all?” checks in automated pipelines.
6. Draftable (Free Tier) — Best Free Online
Strictly speaking freemium rather than open source, but its free online comparison needs no account and handles PDF/Word/PowerPoint — the easiest zero-install option. We include it because “free” is what most searchers actually mean. Try it free
7. LibreOffice Draw — The Manual Fallback
LibreOffice can open PDFs for visual inspection. It’s not a comparison tool — but for a one-off “are these the same?” check, opening both in Draw side by side costs nothing and needs no new software.
When Free Isn’t Enough
Open-source tools cover detection well but not documentation: none produce the formal, filterable change reports that legal, publishing, or audit workflows require. When you need that, see our ranked list of the best PDF compare software — Adobe Acrobat Pro’s Compare Files remains the professional benchmark.
Frequently Asked Questions
Is DiffPDF really open source?
Version 2.1.3 was released under the GNU GPL license — free to use, modify, and distribute. (The later v6 commercial branch was proprietary and is now discontinued.)
What’s the best free alternative to Adobe Acrobat’s compare tool?
DiffPDF for interactive visual comparison, diff-pdf for scripted/Git workflows. Neither produces Acrobat-style formal reports — that’s the main thing you give up by going free.
Are open-source PDF tools safe for confidential documents?
Generally yes — and often safer than free web services: desktop open-source tools process files locally with no cloud involved. That’s a genuine privacy advantage.
Last updated: October 2026. diffpdf.org is an independent resource center, not affiliated with Qtrac Ltd.