Compare PDFs
Find exactly what changed between two PDFs.
Free · No sign-up · Files deleted in 1 hour
How to Compare PDFs
- Add two PDFsDrop a First and a Second PDF, or import from Drive / OneDrive.
- Review the differencesSee an aligned side-by-side or unified diff, jump between changes, and copy what you need.
- Download the reportSave a full PDF comparison report — files are processed securely and deleted automatically.
Compare Two PDFs Online — Free Diff & Highlight Tool
See exactly what changed between two versions of a PDF — additions, removals, and matching lines — without opening both files side by side and eyeballing them yourself.
Upload an original and a revised PDF and Dudle lines them up in an aligned side-by-side view or a unified diff, so you can jump straight between changes instead of reading page by page. Download a full comparison report as a PDF when you need to share what changed with someone else.
Smallpdf has no comparison tool at all and Adobe puts one behind a paid plan — Dudle's compare is free, browser-based, and needs no account, so you're not stuck scanning two tabs manually or paying for a desktop app just to check a contract redline. Both files are capped at 50 MB and are deleted from our servers an hour after the comparison runs.
- Aligned side-by-side or unified diff view
- Jump between changes instead of scanning manually
- Downloadable PDF comparison report
- Compare up to two 50 MB PDFs per job
- No sign-up, no account, files deleted within 1 hour
Frequently asked questions
How do I compare two PDF files for differences?
Upload the original PDF and the revised version, and Dudle generates an aligned side-by-side or unified diff showing everything added, removed, or changed between them.
Is there a free tool to compare PDF documents online?
Yes — Dudle's Compare PDF tool is free and runs entirely in the browser, with no sign-up and no watermark on the downloaded comparison report.
Can I compare a PDF against a Word document?
Not directly — comparison works on two PDFs. Convert the Word document to PDF first with Dudle's Office → PDF tool, then run the comparison.
How do I see what changed between two versions of a PDF?
Upload both versions as the First and Second file. Dudle highlights additions and removals line by line, and you can download the marked-up result as a PDF report.
Can it compare scanned PDFs?
Not directly — comparison reads the text layer, so scanned pages need OCR first (Dudle's Extract Text tool adds one) before a meaningful diff can run.