Upload your original PDF on the left and the updated PDF on the right, then click Find Differences. The tool extracts the text layer from both files using PDF.js and shows every changed line in color-coded diff output. Works only on text-based PDFs - not scanned images.
How to use this tool
Drop each PDF file into its panel, or click to browse. Then click "Find Differences." The tool loads PDF.js on demand (no page-weight cost unless you use the tool), extracts the text layer from both files, and runs a line-by-line diff. Additions appear in green, removals in red.
For large PDFs the extraction step may take a few seconds. The button shows "Extracting text…" while processing. Everything runs in your browser - no files are uploaded to any server.
How PDF text extraction works
PDFs store content in one of two ways: as an embedded text layer (text-based PDFs) or as rasterized images of text (scanned PDFs). This tool uses PDF.js - Mozilla's open-source PDF renderer - to extract the text layer. The extracted text from each page is concatenated and then compared line by line using an LCS (Longest Common Subsequence) diff algorithm, the same algorithm used by Git.
Limitations
PDF text comparison has inherent limitations you should understand:
- Scanned PDFs produce no text. If your PDF is a scan (an image of a printed page), PDF.js cannot extract text from it. You will get empty or minimal output. Use the Image to Text (OCR) tool to extract text from the scan first.
- Text order may differ from visual layout. PDF.js extracts text in the internal order it is stored, which sometimes differs from left-to-right, top-to-bottom reading order - especially in multi-column layouts, tables, or footnotes.
- Formatting is not compared. Bold, italic, font size, and color are not part of the text extraction. Only the character content is compared.
For comparing formatted Word documents, the Compare Documents tool supports .docx files directly.
Use cases
Contract and legal document redlines
When a contract is revised and sent back as a new PDF, paste both versions into this tool to see every changed sentence, clause, or paragraph - without reading both documents in full. Even a single changed word will appear in the diff.
Report and white paper versioning
Compare two versions of a report to verify which sections changed between drafts, which figures were updated, and whether any text was accidentally removed during editing.
Regulatory and compliance submissions
Many regulatory filings, technical standards, and compliance documents are distributed as PDFs. Comparing the current version against the previous one produces a clear audit trail of what changed.
FAQs
Can this compare scanned PDFs?
No. Scanned PDFs contain images of text, not actual text. PDF.js can only extract an embedded text layer. Use the Image to Text (OCR) tool to extract text from the scanned PDF first, then paste the result here to compare.
Is my PDF private?
Yes. All processing runs in your browser using PDF.js. Nothing is uploaded to any server at any point.
What happens with multi-page PDFs?
The tool extracts text from all pages and concatenates them before running the diff. Text from page 1 is compared to text from page 1 of the other document, then page 2, and so on, as a continuous text stream.