How to compare two PDFs
- Choose the original PDF and the changed PDF.
- In Text, pick All pages or a single page to see added and removed words. Pages with changes are marked.
- Switch to Page images for a differences view, a red and cyan overlay, or a side-by-side look.
Lower the sensitivity in the Differences view to catch faint changes, and raise it to ignore small rendering noise.
Questions
Are my PDFs uploaded?
No. Both files are read and compared in your browser. Neither one leaves your device.
What is the difference between Text and Page images?
Text compares the words on each page and marks what was added or removed. Page images compare how the pages look, which also catches changed pictures, layout, and colors, and works for scans.
How do I read the colors?
In Text, red struck-through words are only in the first PDF and green underlined words are only in the second. In the Differences view, red marks are only in the first and green only in the second. Overlay shows cyan for the first and red for the second.
Why does everything look changed after I moved a paragraph?
Pages are compared by number. If text flowed onto a different page, use All pages in the Text view, which compares the whole document as one.
Can it compare scanned PDFs?
Use Page images for scans. Text comparison needs selectable text; run a scan through Image to Text (OCR) first if you need word-level differences.
Credits
Built on PDF.js (Apache-2.0) and jsdiff (BSD-3-Clause). OneTooling is not affiliated with these projects.