Question 1

What is CatchDiff?

Accepted Answer

CatchDiff is an AI-powered PDF comparison tool that compares two PDF documents side-by-side with character-level precision. It uses smart page matching to correctly handle inserted, deleted, and reordered pages — a problem other tools like Adobe Acrobat and Wondershare get wrong.

Question 2

How do I compare two PDFs?

Accepted Answer

Go to catchdiff.com, upload your original PDF and the new version, then click "Compare Documents." CatchDiff extracts the text, matches pages intelligently, and shows you every change highlighted in red (removed) and green (added). No account needed for the first 30 comparisons.

Question 3

Is CatchDiff free?

Accepted Answer

Yes. The free tier gives you 30 comparisons per month with full features including smart page matching, character-level diffs, side-by-side viewer, and PDF export. No credit card required. For unlimited comparisons, the Base plan is $1.99/month with a 14-day free trial.

Question 4

How is CatchDiff different from Adobe Acrobat?

Accepted Answer

Adobe Acrobat compares pages by position — page 1 vs page 1, page 2 vs page 2. If you insert a page in the new version, every comparison after that point is wrong. CatchDiff uses cosine similarity to match pages by content, so insertions and deletions are detected correctly. CatchDiff is also significantly cheaper at $3.99/month vs Adobe's $19.99/month.

Question 5

Can CatchDiff handle scanned or image-based PDFs?

Accepted Answer

CatchDiff detects scanned pages automatically and shows a warning banner. You can run OCR (optical character recognition) directly in your browser to extract text from scanned pages. OCR runs client-side using Tesseract.js — no data is sent to any server. The desktop app bundles OCR for fully offline use.

Question 6

What is the AI summary feature?

Accepted Answer

CatchDiff can generate a plain-English summary of all changes between two PDFs using AI (OpenAI GPT-4o mini or Google Gemini). The summary includes an overview and a list of key changes. You trigger it manually by clicking "AI Summary" — it never runs automatically. The summary is included in exported reports.

Question 7

What does BYOK (Bring Your Own Key) mean?

Accepted Answer

BYOK means you can use your own AI API key from OpenAI, Google (Gemini), or Anthropic (Claude) for AI summaries. This gives you unlimited AI summaries at your own cost. Your key is stored only in your browser's localStorage — it is never sent to or stored on our servers. Get a key at platform.openai.com or aistudio.google.com.

Question 8

What are the pricing plans?

Accepted Answer

Free: 30 comparisons/month, all core features. Base ($1.99/month): unlimited comparisons, OCR, BYOK AI — 14-day free trial. Pro ($3.99/month): everything in Base plus server-side AI summaries — 14-day free trial. Desktop ($1 per machine): one-time purchase, works fully offline, lifetime license with free updates.

Question 9

Is there a desktop app?

Accepted Answer

Yes. CatchDiff has a desktop app for Windows and Linux (macOS coming soon). It works fully offline — no internet required after installation. The trial version gives you 30 free comparisons + 30 watermarked. Purchase a license ($1 per machine) to unlock unlimited use.

Question 10

Is my data safe? Are PDFs stored?

Accepted Answer

No PDFs are stored. Files are processed in memory on the server and deleted immediately after comparison. No document content is ever saved to a database or file system. CatchDiff complies with GDPR and includes a cookie consent banner, privacy policy, and data protection addendum.

Question 11

Can I export the comparison results?

Accepted Answer

Yes. CatchDiff exports to PDF or text format. You can include per-page notes and the AI summary in the export. Four export formats are available: Text Diff, PDF Preview, Text Diff + Notes, and PDF Preview + Notes.

Question 12

Does CatchDiff support multiple languages?

Accepted Answer

The comparison tool UI supports English, Japanese, Portuguese, and Indonesian. The tool compares PDF text in any language — it works with any characters the PDF contains. Landing pages are available in English (/), Portuguese (/pt), Indonesian (/id), and Japanese (/ja).

Question 13

How does smart page matching work?

Accepted Answer

CatchDiff extracts text from each page, computes TF-IDF vectors, and uses cosine similarity to find the best match between pages in the two documents. This means if you insert a new page 3 in the updated document, CatchDiff correctly pairs old page 3 with new page 4 — instead of comparing them by position like other tools.

Question 14

Can I use CatchDiff for legal or compliance document comparison?

Accepted Answer

CatchDiff is widely used for comparing contracts, legal documents, regulatory filings, and compliance reports. The character-level diff catches even single-word changes. However, CatchDiff compares extracted text only — formatting changes, image changes, and handwritten annotations are not detected. Always verify critical changes against the original documents.

Question 15

Is there an affiliate program?

Accepted Answer

Yes. CatchDiff offers a 20% commission affiliate program. You earn 20% on every sale made through your referral link — including recurring subscription payments. Sign up at catchdiff.com/affiliates. Payouts are handled manually (offline).

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