Redaction is the removal or obscuring of certain text before releasing a document to the public. With paper documents, it is pretty simple. Just take a black Magic Marker and color over the text and then make a photocopy of it. Redacting PDF documents doesn’t work quite the same way. Recently the Pentagon released a report in PDF format about the Bagdad shooting of an Italian car spiriting a freed hostage to the airport. Many items, including soldier’s names, were redacted by placing black boxes over them. It was fairly easy for anyone to access the improperly redacted information.
I recently learned from Adobe about some real and effective PDF redaction tools from Appligent.com. The products are not cheap, but if you are redacting a PDF you are going to distribute, you want to do it right.