There have been several embarrassing incidents recently in which information was learned from electronic documents because they were not adequately secured. In some cases, the editing history of a Word document was revealing; in others, text was still readable despite attempts to black it out.
Microsoft has released a tool intended to prevent redaction errors in Word 2003. You can mark text and create a new redacted version of a document in which the marked text is replaced with a black bar that cannot be converted back into text. Here’s the site where you can read about and download the Word 2003 Redaction Add-in.
Don’t forget the companion add-in that removes hidden data and collaboration data from Office documents, available here. If your office uses Word’s features to track changes or exchange comments, this should be routinely run before a document is sent outside the office.