"A PDF Document is a many layered thing." So says Thom Parker, who in this article tries to make sense of the structures and objects that compose a PDF Document with a view to fostering a better understanding of the PDF Specification.
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.