PDF CanOpener provides instant access to information about drawn objects (fonts, color spaces, object location, etc.) as well as a COS level tree view for analysis and manipulation of the internal object structure, plus many other features for low level PDF handling.
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.