Planet PDF talks to Glenn Reid, among other things, expert in PostScript. Glenn has written and published two books with Addison-Wesley on the PostScript Language - one is Adobe's 'Green Book'. Glenn disusses the development of PostScript and its relationship to 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.