Compare PDF

Compare selectable text and inspect PDF pages side by side or as an overlay. Export a readable text-change report.

Unlimited Free Usage

Unlocked PDFs only. Processing stays on your device. Keep the original; editing invalidates digital signatures and may remove forms, annotations, bookmarks or other interactive features.

Choose exactly two PDFs. Visual previews show the same page number in both documents. Text comparison is exact and case-sensitive, not AI semantic comparison. Scan-only files need OCR first.

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File contents and entered text stay on this device. Only access checks and non-content usage metadata go to Helphonic.

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How to use

Compare PDF

Learn how to use Compare PDF: step-by-step instructions, settings, export options, privacy, limits and troubleshooting.

Step-by-step instructions

  1. Choose exactly two unlocked PDFs.
  2. Use the page controls to inspect synchronized page numbers side by side or with an adjustable overlay.
  3. Choose an optional text page range and create the comparison report.
  4. Review added and removed lines, then download the report.
Options and output

Text comparison uses extracted lines, exact case-sensitive matching and a bounded longest-common-subsequence diff. Reading order can differ for columns or complex layouts. The visual overlay is a manual inspection aid, not an automated pixel-difference or semantic AI report. Scan-only documents need OCR before text comparison. If documents differ in length, the preview identifies missing pages.

Compatibility and privacy

Use an unlocked PDF up to 20 MB and 100 source pages. Files and output stay in this browser. Work is not saved after leaving the page. Modifying a digitally signed PDF invalidates its signatures; retain the original. Forms, annotations, bookmarks and document-level interactive features may not survive page rewriting. These tools are not intended to preserve certified or archival conformance.

Review before sharing

Keep the original PDF and check the exported page count, appearance and content before sharing. Browser memory and rendering limitations can prevent a particular PDF from processing; unsupported documents are rejected rather than uploaded elsewhere.

Processing and privacy

Files and entered content are processed on your device in this browser tab. File contents and results are not uploaded to Helphonic or sent to analytics. The page still contacts Helphonic to load its tools, check access and confirm non-content usage information. Work is not saved to your account; download or copy results before leaving or reloading the page.

If an operation cannot finish

Use a current browser and smaller inputs if the tab runs out of memory. Some tools download a local processing library or model on first use, so an internet connection is needed even though your content stays on the device.

If the tool reports that access or limits changed, review the current policy and run it again. If usage confirmation is uncertain after an interrupted connection, a retry can count as another operation. Download completed work before reloading; this site does not keep a recovery copy.

About this tool

Text comparison uses extracted lines, exact case-sensitive matching and a bounded longest-common-subsequence diff. Reading order can differ for columns or complex layouts. The visual overlay is a manual inspection aid, not an automated pixel-difference or semantic AI report. Scan-only documents need OCR before text comparison. If documents differ in length, the preview identifies missing pages.

Read the full Compare PDF guide (opens in a new tab)