In a recent post I joked about hiding sensitive text in a Word document by formatting it as 1-point white-on-white Wingdings. Well I just stumbled across a post on SecurityFocus from late October that talks about a similar gaffe where someone released a document as a PDF. They used the Word "highlight" tool to paint a black background on the document, hoping that it would be enough to hide the information from readers.

Maybe if they'd printed it out it the trick would have helped, but not when they distributed the raw bits to people electronically. Be very careful in how you deal with sensitive electronic documents!