How to use Compare PDF
- Select exactly two unencrypted PDFs: the before document, then the after document.
- Check the before and after previews. Use Swap before and after if the order is wrong.
- Choose Compare PDF to compare matching page positions.
- Review added, removed, changed, and unchanged page pairs. Download the comparison ZIP with difference images and a UTF-8 text report.
Worked example
A typical document-processing workflow.
Input
Before: Project Alpha. After: Project Beta, with one extra page.
Output
A changed page pair, an added trailing page, red visual differences, and extracted-text additions/removals.
Pages are paired by position. An inserted page can change the alignment of later pairs; the tool does not infer semantic page matches. Scanned pages without a text layer use visual comparison without OCR.
What the tool does
Pages are paired by position. An inserted page can change the alignment of later pairs; the tool does not infer semantic page matches. Scanned pages without a text layer use visual comparison without OCR.
All document processing happens in your browser. No PDF or image contents are sent to the tool API. Keep your original files and review every downloaded result.
Interpreting differences
Visual comparison highlights changed pixels in red. Rendering and font differences can produce highlights, so inspect the before and after previews rather than treating a match as proof that documents are equivalent.
Text changes come from extracted PDF text with normalized whitespace. Pages without a text layer are reported as visual-only; no OCR is performed. Very large text changes use an explicit full-text fallback rather than an unbounded word comparison.
Limits and supported files
The combined input limit is 50 MB. Rendering jobs process up to 100 pages or images, with at most 12 megapixels per rendered page or input image and 100 MB of accumulated encoded output. Choose fewer pages, a lower output DPI, or smaller images if a limit is exceeded.
Encrypted, corrupt, empty, and unsupported documents are rejected. XFA forms are unsupported. Large or complex files may exceed your device memory even within the stated limits. You can cancel processing; changing inputs or output settings clears previous download results.
The 100-page processing limit counts pages in both documents together. For example, two 50-page PDFs use the full allowance for one comparison job.
Frequently asked questions
Are my files uploaded?
No. The PDF utility processes selected files in your browser and creates downloads on your device.
What happens if processing is cancelled?
No completed download is published for the cancelled operation. Your original files remain unchanged; you can run the tool again.
Does this work with protected PDFs?
Encrypted PDFs are unsupported. Use an unencrypted copy you are authorized to process.