Steve Aftergood of the Federation of American Scientists has posted the US National Security Agency's guide to Sanitizing Word and PDF docs.
Section 2: Procedures to Sanitize a Word Document
The following steps were tested with MS Word 2000 and Acrobat 5.0 and 6.0. Other recent
versions should work similarly. While time-consuming, these steps give the highest confidence
that sensitive information is not hidden in the released document. Copying the text and images
into a blank document is a good way to manually review a sensitive document, since sections can
be copied over one at a time as they are reviewed.