Ted Padova, author of the Acrobat PDF Bible, provides a detailed (17 parts) step-by-step guide on creating and using Acrobat PDF Forms. Many of the resources and examples cited in his article are also available for download.
It's usually a good idea to initialize variables with sane values as soon as they are created (and sanity-check incoming argument values before using them). Intialize your form fields to rational values. Don't just leave them blank or zero. If you do, you don't know what kind of nonsense might happen.
Kas Thomas reflects on where he thinks Acrobat and PDF are headed, and on where they fit in the greater communications technology picture. Agree or disagree? Post your thoughts on the future of PDF in the Planet PDF Forum!
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.