Preventing Changes

Hmm, not sure why you asked this in the Photoshop forum. Adobe offer redactions for PDFs, in Adobe Acrobat. What type of material do you have?

Not if the redaction is properly performed with a redaction tool. These must remove all content from that area of the page, whatever it is (text, scan, outline, anything). Some people "redact" with simple masks, which works as well as you'd imagine. (Glossary. How to Redact | ShareVault has this story: "For example, in 2008, a ...employee failed to properly redact a 93-page operating manual detailing ...screening procedures. The manual was posted on a government-procurement website where with a simple copy and paste anyone who was interested could read about which passengers are more likely to be targeted for secondary screening, who is exempt from screening, ...procedures for screening foreign dignitaries....")