Compare Two PDF Files and Find Differences
Visually compare two PDF files and highlight what changed, page by page.
How to Compare Two PDF Files in 3 Steps
- Upload your two PDF files. Select both the original PDF (File A) and the revised version (File B) using the two upload areas. Both files must be PDFs.
- Click "Compare PDF". PDFTools rasterizes both PDFs and uses ImageMagick's comparison engine to produce diff images showing exactly which regions differ between the two versions. Changed areas are highlighted in red.
- Download the diff result. Receive one diff image per page showing the differences highlighted in red. Single-page comparisons return one image; multi-page comparisons return a ZIP of diff images.
Why Use PDFTools to Compare PDF?
- Visual difference highlighting — Changed regions between the two PDF versions are marked in red on the difference image, making it immediately clear what has changed at a glance.
- Page-by-page comparison — Each page of the two documents is compared independently, producing one diff image per page so you can pinpoint exactly which pages changed.
- Works on any PDF type — Compare contracts, reports, design documents, presentations, and any other type of PDF — the comparison works on the rendered visual output of the pages.
- Useful for document review — Commonly used to verify that a final signed version matches the draft, check that a translated document has the same layout, or review revisions in contracts and proposals.
Frequently Asked Questions
What does the red highlighting in the comparison image mean?
Red highlighted areas indicate pixels that differ between File A (original) and File B (revised). This includes added text, deleted text, moved elements, and changed images. A completely red page means the two pages are entirely different; white areas mean those regions are identical.
Can the comparison tool detect text-level changes?
The comparison is visual — it compares the rendered appearance of the two PDFs at the pixel level, not the underlying text data. This means it will detect any visual change including text edits, formatting changes, and image differences. However, it cannot tell you specifically which words changed — it shows you where on the page things look different.
What if the two PDFs have different numbers of pages?
PDFTools compares pages that exist in both documents. If File A has 5 pages and File B has 7 pages, only the first 5 pages are compared. The additional pages in File B that have no corresponding page in File A are noted but not compared.