When you send a PDF, you send more than the pages. A PDF carries a small set of fields describing the document, and it can carry comments, form data, attachments and leftovers from earlier edits. Most of it is harmless. Some of it is the kind of detail you would never put on the page deliberately: your full name when you meant to be anonymous, the name of a client you were not supposed to mention, or the fact that a "final" report was created two years ago.
The document information fields
Almost every PDF has these, filled in automatically by the software that created it:
- Author is usually the name of the user account on the computer, or the name registered in Word. On an office computer that might be a colleague's name, or "Admin".
- Title is often the document's title, but some print drivers fill it with the original file name, such as "Microsoft Word - Draft 4 offer for competitor.docx".
- Creator and Producer name the software and its version.
- Creation and modification dates record when the document was made and last changed, to the second.
- Subject and Keywords are rarely set, but when they are, they can hold notes nobody meant to share.
Open any PDF in PDF metadata to see these fields, change them or clear them.
Where metadata causes real problems
Anonymous submissions. Peer review, whistleblowing, anonymous feedback and blind job applications can all be undone by an Author field holding your name.
Reused templates. A proposal built from last year's proposal for a different client may carry that client's name in its Title or Subject.
Dates. A document presented as freshly prepared, but with a creation date years earlier, invites questions. So does a "signed on the 3rd" document modified on the 9th.
Hidden content beyond metadata
Comments and annotations made during review can stay in the file even when the reader you use hides them. Flatten PDF in image mode removes anything that is not visible on the page.
Covered text. Text hidden under a black or white box is still there. This is the most damaging leak of all; see how to black out text so it stays hidden.
Earlier versions. Some editors save changes by appending them to the end of the file rather than rewriting it, so earlier content can survive inside. Re-saving through a tool that rebuilds the file, such as most of the tools on this site, drops these leftovers.
Extra pages. A "summary" taken from a long report is sometimes the long report with most pages hidden in a viewer's thumbnail panel, or simply forgotten at the end. Remove what you do not mean to send with Delete pages.
A sixty-second check before sending
- Open the file in PDF metadata. Clear or correct the author, title and subject.
- Scroll through every page. Is anything there you did not mean to include?
- Press Ctrl+F and search for a name or number that should not appear.
- Check the file name: final-v2-real-for-boss.pdf reveals more than you think.
Prevention is easier than cleaning: in Word, File, Info, Check for Issues, Inspect Document removes personal information before you export.