Impress enables text impressions to be stamped to a range of pages in a PDF file. This can be set either as a watermark which is on a layer below all of the existing text and images or above where it can be used for headers and footers, page numbering etc. Variables can be set to define page numbering, total number of pages and date and time.
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.