P/Comp is an Acrobat Plug-In for comparing versions of PDF files. Using P/Comp will build bookmarks and links that describe the differences between two PDF files. P/Comp uses different colors of links to highlight differences in font types, size, position, and most importantly, new or missing words. Bookmarks are organized into New Words and Missing Words by page in the PDF.
OK, so you want to stamp your document. Maybe you need to give reviewers some advice about the document's status or sensitivity. This tip from author Ted Padova demonstrates how to add stamps with the Stamp Tool along with related comments.