Manual editing of PDF files is extremely difficult
or impossible. PDF is a binary format and traditional text editors are
poorly equipped to handle the sophisticated graph structure of a PDF
document. Moreover, PDF data streams can be encrypted and compressed in
variety of ways so that manual editing is not possible. pdfTron CosEdit
automates the task of low level PDF editing. It is a stand-alone, low
level, PDF editor. It is an essential power tool for professionals working
with PDF, FDF, PJTF.
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.