The free Acumen Journal presents two monthly articles, one -- "The Acrobat User" -- featuring advanced uses of Adobe Acrobat, and the second -- "PostScript Tech" -- covering some aspect of PostScript programming.
For September, the technical features by John Deubert of Acumen Training are:
Deubert shows how to create a PDF-based shareware document that repeatedly asks for money. If ignored, the document becomes increasingly strident, eventually rendering itself unreadable.
PostScript Tech: "Colorizing Images with Separation and DeviceN"
He presents a useful, though little-known technique, using the Separation and DeviceN colorspaces to modify image colors. Among other things, this allows us to simulate printing images on a colored background.
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.