How to compare two PDF files
Updated
Contents
To compare two PDF files, open Compare PDF, pick the two versions, and select Compare PDFs. You get their page counts, the size difference and every line of text that was added or removed, plus a report you can download. It runs in your browser, so both files stay on your device.
The comparison reads the text in each PDF, line by line. That makes it good at the question most people are asking — what changed in the wording — and blind to changes that are only visual.
Step by step
- 1Open the Compare PDF tool.
- 2Pick two PDFs — the first is treated as the original, the second as the revised version. Both stay on your device.
- 3Select Compare PDFs.
- 4Read the summary: the page counts, the size difference and the number of changed lines.
- 5Review the lines marked removed (-) and added (+).
- 6Download the comparison report as a .txt file.
What counts as a change
A line of selectable text that is in one PDF and not the other. Lines only in the first PDF are listed as removed, and lines only in the second as added. Extra spaces inside a line and blank lines are ignored, so reflowed spacing does not flood the report.
Because the first file is the original, the order you pick them in matters: swap them and every addition becomes a removal.
Scanned PDFs need OCR first
Compare PDF reads the text already embedded in each PDF. A scanned page is a picture with no text in it, so two scans compare as having no selectable text at all. Run each one through OCR PDF first — it adds a searchable text layer on a secure server — then compare the results.
What it does not compare
Formatting, images, colors and layout are not compared — this is a text comparison, not a visual one. To read one file's text on its own, PDF to Text extracts it as a plain .txt file.
Common questions
Does the order of the two files matter?
Yes. The first file is treated as the original and the second as the revised version: lines only in the first are listed as removed, and lines only in the second as added.
Why does it say no selectable text was found?
Both PDFs are most likely scans, which carry pictures of text rather than text. Run them through OCR PDF first, then compare the results.
Do my files leave my device?
No. Compare PDF runs entirely in your browser, and both files stay on your device from start to finish.
How large can each PDF be?
Up to 100 MB per file.