A counterparty sends "a few small updates" to a contract as a fresh PDF, with no tracked changes. Before AI, you ran a document comparison and read the redline line by line. Now you can ask an AI assistant: "What changed between these two versions, and does any change shift risk to us?" It is fast and often insightful. It also misses things a dumb comparison never would.
What AI is good at here
- Explaining the meaning of a change. A redline shows that "shall" became "may". AI can tell you that turns an obligation into an option.
- Spotting knock-on effects. A changed definition can alter every clause that uses it; AI can trace that.
- Summarising for non-lawyers. "The supplier now has 60 days to fix defects instead of 30, and liability is capped at fees paid in the last 6 months instead of 12."
- Prioritising. It can rank changes by likely importance so you read the risky ones first.
What AI can miss
- Small, exact edits: a number, a date, a decimal point, "not" inserted in a long sentence.
- Moved text. Clauses reordered or relocated can be reported as deletions and additions, or not at all.
- Changes in tables, schedules and footnotes.
- Formatting-based changes, such as text struck through but still present.
- Confident omissions. A model may summarise "no other material changes" when it simply did not notice one.
The failure mode is dangerous because the output reads authoritatively.
A workflow that uses both
- Run a deterministic comparison first. Use a document comparison tool (Word's Compare, Acrobat's Compare Files, or a dedicated tool) to produce a full redline. This is your source of truth. See how to compare two PDFs.
- Give the AI the redline, not just two PDFs, and ask it to explain each change and its effect.
- Ask for exact quotes of old and new text for every change, so you can check them against the redline.
- Read every change in the redline yourself for anything material: money, dates, liability, termination, IP, data.
- Record your decisions on each change. See writing a decision log.
Prepare the documents
- Make sure both PDFs have real text, not scans. Run OCR if needed. See how to make a PDF searchable.
- Remove signature pages and cover sheets that differ only cosmetically.
- If schedules or exhibits are separate files, compare them separately.
Confidentiality
Contracts often contain confidential commercial terms. Use an AI tool your organisation has approved, on a plan that does not train on your data, or a local model. See local AI vs cloud AI for PDFs and risks of using AI on confidential PDFs.
After agreement
Once the final version is agreed, lock it down: export the final PDF, sign it, and store it as the executed copy. Any later "clean-up" edits create a third version and restart the problem. A browser editor such as Docento.app can add signatures and initials without uploading the contract.
Takeaway
Let a comparison tool find every change and let AI explain them. Never let AI be the only thing standing between you and a quietly edited clause. For the broader process, see contract lifecycle management explained.
