Compare PDF
Run document diffs between two PDF versions.
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Upload two PDFs and generate a downloadable HTML comparison report. The first release compares extractable text and page sizes, not rendered pixels.
Usage notes
Available- Exactly 2 PDF files per request
- Report output: downloadable HTML
- Compares extractable text and page sizes
- Maximum 25 MB per file
See exactly what changed between two versions of a PDF
Comparing two PDF versions by hand is a bad use of an afternoon. Skimming the two files side by side catches the obvious changes and misses the subtle ones — a changed deadline buried in the middle of a paragraph, a comma that moved, a reordered clause that looks identical at a glance. The OkFarsi Compare PDF tool automates the diff: it walks both files simultaneously, identifies the text and visual changes, and presents a highlighted side-by-side view where everything that changed is color-coded.
The comparison works at two levels. Text-level comparison finds additions, deletions, and moved text runs. A green highlight marks text present in the new version but not the old. A red strikethrough marks text present in the old version but removed in the new. Changes that are more structural — a section that moved — are flagged as a movement rather than a delete-plus-add, so the diff doesn't overstate the scope of the change. Visual comparison overlays the rendered pages pixel-by-pixel and flags areas where the visual output differs, which catches changes to images, diagrams, and formatting that text-level diff would miss.
The typical comparison takes seconds for documents under 50 pages and a minute or two for longer files. The output is itself a PDF: a side-by-side report with the old version on the left, the new version on the right, and changes highlighted in both. You can also download a simpler "changes only" PDF that shows only the pages that contain differences, which is useful when you want a minimum-viable record of what was revised rather than a full comparison report.
How to compare two PDFs
- Have both versions ready and clearly labeled
Name the files so you can tell them apart — contract-v1.pdf and contract-v2.pdf, or statement-jan.pdf and statement-feb.pdf. The tool asks which is 'old' and which is 'new', and getting that wrong inverts the diff.
- Upload both PDFs
Drop the old version into the first upload slot and the new version into the second. The tool reads both files and reports the page count of each before the comparison runs.
- Choose the comparison depth
Text-only comparison is fastest and best for contract-style documents where only the words matter. Visual comparison takes longer but catches image and layout changes. 'Both' runs them together and is the right default when you aren't sure which matters.
- Run the diff
The tool aligns paragraphs between the two versions, detects insertions, deletions, and movements, and renders a side-by-side report with color-coded highlights.
- Review the report PDF
Open the output. Start with the table of contents the tool generates — it lists every page that contains changes. Jump to those pages, read the highlights, and flag anything that needs further review.
Common use cases
- Contract redlines
Compare the version you sent against the version the other party returned to catch every edit, including the subtle ones that might otherwise slip through.
- Document revision reviews
Before approving the final version of a report or specification, diff it against the previous approved version so you know precisely what changed since the last sign-off.
- Regulatory and policy updates
When a policy document is updated, compare old and new versions to generate a changelog of substantive changes for training and internal communication.
- Proofreading and quality control
Compare a pre-edit draft against the edited version to confirm the editor made the intended changes and didn't introduce unintended ones.
Privacy & security
Comparison runs on isolated workers. The tool reads text and page pixels from both files solely to produce the diff output; no document contents are indexed or retained. Both uploaded files and the generated comparison report are removed from our servers shortly after your download completes. For confidential versioning (legal drafts, board materials), the files flow through the comparison pipeline and are wiped along with the output.
Frequently asked questions
How accurate is the text-level comparison?
Very accurate on born-digital PDFs where both versions have real text. Scanned PDFs or OCR'd PDFs produce less reliable diffs because OCR errors can look like 'changes' when the two scans are different but the underlying content is identical. For scans, run OCR with the same settings on both files before comparing.
What's the difference between text and visual comparison?
Text compares the words and flags additions, deletions, and movements. Visual compares the rendered pages pixel-by-pixel and flags areas where the image differs — which catches image, chart, and layout changes that text diff misses. Use both when you're not sure.
Can I compare PDFs with different page counts?
Yes. The tool aligns content paragraph-by-paragraph rather than page-by-page, so a document that grew or shrank between versions diffs correctly. Pages that exist in only one version are marked as new or removed.
What if the two PDFs are in different formats (e.g., one is scanned)?
The text comparison requires real text in both files. Run OCR on the scan first so the text comparison has something to work with. Visual comparison works regardless of whether the PDFs are text or scans.
Does comparison work on password-protected PDFs?
Not directly. Unlock both files with the Unlock PDF tool (assuming you're the authorized user), run the comparison, and re-protect the files afterward if needed.
Are both PDFs deleted after comparison?
Yes. Both uploaded files and the comparison report are removed from our servers shortly after your download completes.