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Redline diff with AI severity analysis.
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What you'll get: a side-by-side diff of two PDFs with added / removed / changed text highlighted, plus a plain-language summary of what changed. For another use, try AI · Redact PDF.

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Private & secure
AI tools process your PDF in memory, send only the extracted text to the model, and discard everything immediately. No file is persisted on our servers.
No watermarks
Clean output, no branding, no daily limits.
Pay only for what you use
Purchased credits never expire. Cancel anytime.

Why people compare PDFs semantically

Pixel-level diff (PDF Compare) shows you WHAT changed — the visual differences between two versions. Semantic compare goes deeper: it tells you what those changes MEAN. Added clauses, removed sections, reworded definitions, shifted commitments. The difference between “something changed” and “here’s what to flag for legal.”

Contract redline review
Counter-party returns a marked-up MSA. AI Compare summarizes what changed in plain language — e.g. “liability cap increased from $500K to $2M; payment terms changed Net-30 to Net-60; new indemnity clause section 8.4.” Use as the input for your “is this acceptable?” review.
Document version reconciliation
Two purportedly-same PDFs from different sources — the “executed” vs the “draft.” Find the actual content differences, not just whitespace or formatting drift that pixel-diff would surface.
Research paper revision tracking
A journal asks for a revised version. Compare draft v1 vs v2 to summarize what was added in response to peer review. Useful as input for the cover letter to the editor.
Translation back-check
Translate doc to language X, then back to source. Compare original vs back-translated to surface places where the translation drifted semantically. Good QA pass for high-stakes translations.
Policy / handbook diff
Employee handbook v2024 vs v2025. AI Compare summarizes what changed in plain language — useful for the change-summary email to all employees.

How AI Compare works

Three steps. Sign in to run, zero retention — files never persisted on our servers.

  1. STEP 1
    Drop two PDFs
    Document A (original / before) and Document B (revised / after). Both up to 100 MB.
  2. STEP 2
    We extract + chunk-align + diff
    Server-side text extraction from both, then a chunk-alignment pass to match corresponding sections, then a semantic-diff prompt that summarizes additions, removals, and modifications in plain language.
  3. STEP 3
    Get a structured diff report
    Markdown output organized by section: “Added in B,” “Removed from A,” “Modified.” Page citations included so you can verify each finding against the source.

What makes pdfcraft ai different

  • Citations on every claim
    Every AI summary, answer, and translation links back to the page it came from. You can verify the source before relying on the output. Hallucination is bounded, not blind.
  • Pay only for what you use
    No subscription. Purchased credits never expire. Cancel anytime. Cost shown before you run — exact credit amount appears after upload.
  • Multi-provider routing, no vendor lock-in
    We balance multiple AI providers per call to optimise cost and quality. If one has an outage, the next call automatically tries another. You're not bound to a single vendor's pricing or downtime.
  • Zero retention by design
    Your PDF lives in memory only as long as the AI call needs it, then it's discarded — nothing is persisted to our servers. We don't fine-tune models on your data. Verifiable in your dashboard's audit log.
  • Honest about model limits
    When a doc exceeds the model's context window we surface that the output was truncated (we render result.wasTruncated in every AI tool's UI). When a number can't be verified from the source we flag it. No silent failures.

Frequently asked questions

How is this different from PDF Compare (pixel diff)?
Pixel diff (free tool /tool/pdf-diff) tells you WHERE pages look different — red highlights on changed regions. AI Compare tells you WHAT semantically changed — added clauses, reworded definitions, etc. They’re complementary: pixel diff catches layout shifts; semantic diff catches content shifts. For thorough QA, run both.
Does it work on PDFs with very different formatting?
Better than pixel diff would — semantic compare normalizes formatting before alignment so a Word-export-A vs a Google-Docs-export-B with the same content produce a near-empty diff. Pixel diff would scream every page red.
What if the documents are mostly identical?
Output explicitly says so: “No semantic differences detected.” Trivial formatting diffs (whitespace, font choice) don’t pollute the report.
What if they're completely different documents?
The output flags the alignment as failed and reports the inputs as unrelated. Tool isn’t useful for unrelated content; that’s a use case for AI Summarize on each separately.
What's the credit cost?
8 credits per compare (more than Summarize because two inputs are processed + aligned).
Can I rely on the diff for legal review?
Use as a navigation aid, not as the review itself. The diff tells you WHERE to look; a lawyer reads the actual clause changes. LLMs occasionally miss nuance in legal language; verify high-stakes findings against the source.

Need pixel-level visual diff too?

PDF Compare (visual) shows the regions of each page that look different — red highlights on changed pixels. Pairs naturally with AI Compare (semantic) for thorough document QA.

Try PDF Compare

Related PDF tools

Other tools in the AI category — built on the same private, in-browser pipeline.

Use cases for this tool

Step-by-step workflows that put this tool to work.

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