About Compare PDF

Comparing two versions of a PDF document is essential for contract review, document auditing, and quality control workflows. When a contract has been revised, a report has been updated, or a design has changed, knowing exactly what is different between two versions saves significant time and prevents errors.

LocalPDF's Compare tool renders both PDFs page by page and performs a pixel-accurate visual comparison. Differences are highlighted in red on a combined view, giving you an instant visual map of every change. The comparison summary shows how many pages changed and the overall percentage of content that differs.

The entire comparison process runs in your browser using pdfjs-dist for rendering and a canvas-based pixel diffing algorithm. Neither document is uploaded anywhere.

How to Use

  1. 1Upload the original document in the "Original Document" slot.
  2. 2Upload the revised document in the "Revised Document" slot.
  3. 3Click "Compare Documents" to begin the page-by-page analysis.
  4. 4Review the diff results: red areas indicate changes, dimmed areas are unchanged.
  5. 5Use the page navigation to review each page of the comparison.

Key Features

Visual Pixel Diff

Differences are highlighted in red with unchanged areas dimmed for clear contrast. Instantly see what changed and where.

Page-by-Page Review

Navigate through each page of both documents with side-by-side original, revised, and diff views.

Change Summary

See at a glance how many pages changed, what percentage of content differs, and how page counts compare between versions.

No Upload Required

Both documents are loaded and compared entirely in your browser. No server sees your confidential documents.

Frequently Asked Questions

How accurate is the PDF comparison?

The comparison is pixel-accurate to the rendered view. Minor rendering differences between fonts or rendering engines may show as small changes. Content differences like edited text, moved images, or changed layout are clearly visible.

Can I compare PDFs of different page counts?

Yes. If one PDF has more pages than the other, extra pages are shown as fully different with no matching page in the other document.

Can I compare password-protected PDFs?

Password-protected PDFs must be unlocked first. Use LocalPDF Unlock to remove the protection before comparing.

Why are minor differences showing on pages that look the same?

Sub-pixel rendering differences can cause pixel-level changes in text anti-aliasing. These appear as very faint noise in the diff view and are not meaningful content changes.