"Acrobat" is now the name reserved for Adobe's for-sale PDF creation and management software; Acrobat Standard and Acrobat Professional. You can learn more about these applications here.
Why you should upgrade to the latest version of Adobe Reader - Version 6.01
As Adobe continues to develop the PDF specification, adding new capabilities to the PDF format, they also improve the Reader to improve the user experience and take advantage of new technologies. With Reader 6.01, users benefit from...
An all-new search capability that makes it easier to locate words and phrases in a PDF
Improvements to bookmarks for navigation purposes
Improved support for multimedia features, including embedding of movies in PDF
Improved accessibility for disabled users
However, one of the most important reasons to upgrade is the obnoxious little dialog older Reader users see whenever they view a PDF file created or saved using Acrobat 6.01.
Yes, Adobe wants you to use the new software. No surprise there. Having said that, it is free, and overall, it's an improvement.
If you recognize this window, and if you don't want to see it again (whatever the checkbox says), then we can only suggest you download Reader 6.01 now! You'll be glad you did.
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.