Compare PDF
Spot every difference between two PDFs.
Original PDF (file A)
Changed PDF (file B)
About Compare PDF
Compare PDF reads two versions of a document and shows exactly what changed, page by page, with the lines that only exist in the new file highlighted in green and the lines that only exist in the old one struck through in red. Reviewing revisions this way beats opening two tabs and hopping between them: nothing slips past when a clerk edits a single digit inside a clause on page fourteen. The tool reconstructs the text of each page, aligns the pages of both files in order, and runs a line level diff across every pair, then totals the additions and deletions and lists which pages actually changed. Scanned documents carry no text layer, so the tool warns you when a file looks like a scan and points you to OCR instead of showing an empty diff. Options to ignore whitespace and letter case help when the only real question is whether wording changed, not formatting.
How to Use Compare PDF
Load both versions
Drop the original into picker A and the revision into picker B. The names and sizes of both files are shown so you can confirm you picked the right pair before running.
Set the comparison options
Ignore whitespace hides changes that are only spacing, and Ignore case hides capitalization edits, so the report focuses on words that genuinely changed meaning.
Read the page by page report
Each page becomes a section with its own added and removed counts. Changed pages open expanded and show the diff with line numbers; identical pages stay collapsed so you can skim to where the action is.
Download the change report
Save a plain text report listing every addition and deletion per page, ready to paste into an email or attach to a reply when you send back your comments.
Why Use Compare PDF: Common Use Cases
Contract and agreement reviews
Check the final draft against the version you negotiated and confirm no clause quietly shifted, a number changed, or a paragraph disappeared between rounds.
Invoice and statement audits
Compare the reissued invoice or financial statement with the original to verify that only the promised fields changed and totals still add up.
Thesis and report revisions
See what an editor or supervisor actually altered in your document revision instead of guessing, then accept or argue each change with evidence.
Version control for non programmers
Writers and analysts get the same kind of diff view developers use, without installing anything or learning a version control system.
Compare PDF Specifications
| Input Formats | PDF, PDF |
|---|---|
| Output Formats | On-screen diff, TXT report |
| File Size Limit | No strict limit (dependent on device memory) |
| Processing Engine | 100% Client-side (Runs locally in your browser) |
| Data Retention | Files never leave your device |
| Batch Processing | Single file processing |
Tips for Compare PDF
Scanned PDFs have no text layer, so run them through OCR PDF first; otherwise the comparison reports them as empty.
For plain text or code you can paste directly, the Diff Checker compares pasted content the same way.
When two drafts differ only by layout, enable both ignore options to filter out cosmetic noise and surface real wording changes.
Combine with Merge PDF when the fix is to replace pages: compare first, then assemble a new file from the best pages of both.
Frequently Asked Questions
Does the comparison see images and formatting?
No. It compares the text layer of the two files line by line. Swapped images, font changes, and color edits do not appear in the diff, since the tool reads text rather than pixels.
What happens when the files have different page counts?
Pages are aligned by position. A page that exists in one file but not the other shows up entirely as added or removed, and the summary chips display both totals so the mismatch is obvious.
Why does my scanned PDF compare as empty?
A scan is a picture of text, so there is nothing for a text extractor to read. The tool detects this and suggests running the file through OCR first; after that, the comparison works normally.
How large can the PDFs be?
There is no fixed limit. Both files are processed in your browser, so the practical bound is your device memory. Very dense pages fall back to a plain before and after listing instead of a fine grained diff.
Are my documents uploaded to a server?
No. Text extraction and diffing run entirely in the browser. The files stay on your machine, which matters for contracts and other confidential papers.