You send a draft contract as a DOCX so the counterparty can mark it up. They redline it. You accept changes, finalise, and send the final as a DOCX. Three weeks later you discover the file you signed contained a deleted comment from your colleague calling the counterparty's lawyer "glacially slow".
Format choice has consequences. Here's the rule.
Send DOCX for negotiation
While a document is being negotiated, DOCX is correct. Both sides need to redline, comment, and track changes. A PDF in the middle of negotiation forces the counterparty to retype changes — slow, error-prone, and annoying. Send the working version as a DOCX with track changes on.
Send PDF for execution
Once the document is finalised, execution copies go out as PDF. PDF locks formatting, makes tracked changes and comments inaccessible (if flattened), and is the format every signing tool expects. Convert Word to PDF and flatten the output before sending. Never send a DOCX as the execution version — too much risk of residual comments.
The middle-ground trap
Sending a DOCX as a "final" without flattening or stripping metadata is where most leaks happen. Tracked changes that were accepted but not properly cleared. Comments from internal review. Author tags revealing who drafted what. If you must send a DOCX as final, accept all changes, delete all comments, and clear document metadata before sending. PDF avoids the whole problem.
Court filings: PDF, always
Every court portal in England, Wales, Scotland, and most US jurisdictions accepts PDF as the standard filing format. Some accept DOCX as well, but PDF is the default. File as PDF, keep the DOCX as the working source. If the court wants to mark up the filing, that's their problem, not yours.
FAQ
Should I send a contract for signing as DOCX or PDF?
Always PDF. Signing in DOCX is unsupported by most signing platforms and risks residual track changes leaking through.
Can I track changes in a PDF?
Not in the same way as DOCX. PDF annotations and comments can be added but aren't a substitute for full track changes during negotiation.
What's the safest way to send a DOCX externally?
Accept all changes, delete all comments, inspect and clear document metadata. Better still, convert to PDF for the final version.
Do I need to flatten the PDF after converting?
For execution copies, yes — flattening ensures comments and annotations can't be removed by the recipient.
DOCX for redlining, PDF for execution. Don't blur the line. Convert your final draft cleanly and the deleted-comment surprises stop happening.