My fixation on pricing is justified, I think, because this is a software review, and the only question is whether you are going to receive $170 worth of value to upgrade your copy of Acrobat Professional, or $535 worth of value to buy it new. Owning a version of Acrobat Professional is essential for everyone in the graphic arts: a brand new copy of V7 is available on eBay for CDN$250 to $300 -- a real value! To provide a clear voice in all of this, Adobe created 10 Lettermanesque reasons why you need to buy Acrobat 8 Professional:
Enable advanced features in Adobe Reader
Anyone using free Adobe Reader software (version 7.0 or 8) can participate in document reviews, fill and save electronic forms offline and digitally sign documents.
Combine and optimize documents
Combine documents, drawings, and rich media content into a single, polished Adobe PDF document. Optimize file size.
Accelerate document reviews
Send documents for review and track which reviewers have contributed feedback. Compile comments into a single PDF document with one-button ease.
Save in Microsoft Word
Save Adobe PDF files as Microsoft Word documents, retaining the layout, fonts, formatting, and tables, to facilitate reuse of content.
Create advanced forms
Design dynamic, interactive forms to collect and aggregate data through e-mail or on the Web with included Adobe LiveCycle Designer software. (Windows only)
Easily create Adobe PDF documents
Create Adobe PDF documents with one-button ease from Microsoft Office applications. Windows users can also create Adobe PDF documents from Outlook, Internet Explorer, Project, Visio, Access, Publisher, AutoCAD, and Lotus Notes files.
Apply passwords and assign permissions
Restrict access to Adobe PDF documents using 128-bit encryption.
Permanently remove sensitive information
Permanently remove metadata, hidden layers, and other concealed information, and use redaction tools to permanently delete sensitive content.
Archive papers and e-mails for easy search and retrieval
Scan paper documents with OCR technology to create compact, searchable Adobe PDF documents. Archive Microsoft Outlook e-mail to Adobe PDF.
Generate professional, print-ready files
Automate the preflight process and correct issues that might compromise print quality without creating a new Adobe PDF document.
Not all of these features are available in all versions (as a chart reveals on the company's website). However, every one of these features is already available in Acrobat 7, in most cases from Adobe itself, in two cases from third-parties. What the upgrade affords is some additional robustness in most of the stated features, rather than new features per se.
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.