Foxit Reader is a multilingual freemium PDF tool that can create, view, edit, digitally sign, and print PDF files. The Windows version allows annotating and saving unfinished PDF forms, FDF import/export, converting to text, highlighting and drawing.
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.