Full Disclosure: Security Risks in Using Digital Documents

Editing tips from the NSA | CNET News.com: "Hiding confidential information with black marks works on printed copy, but not with electronic documents, the National Security Agency has warned government officials."

You may or may not know that Microsoft Word embeds a ton of information in your Word documents without your explicit knowledge: things like the date, author (as it was input when Word was installed), and other collaboration and tracking data. A lot of this is stored in "metadata" inside the document.

The article above from the National Security Agency lists recommended procedures for sanitizing documents prior to sharing them digitally or prior to converting them to PDF files.
Interesting read. If you don't have time to read the whole thing, at least go get Microsoft's add-in for Office so that you can review and delete metadata you don't want to share. It's called "Remove Hidden Data" and is for Office 2003 and XP.

Microsoft "Remove Hidden Data" add-in for Office