Update - Chad P. pointed me towards a matrix that compares the Standard, Pro and Extended: http://www.adobe.com/products/acrobat/matrix.html

In working on modernizing some old PDF's, I've had to get a copy of Adobe's new Acrobat 9. We needed to use the Pro Extended to get some of the features that weren't there in lesser versions (Pro and Standard). After doing a bit of searching, however, I wasn't able to pull up a list that quickly compared the different feature sets. Below is a quick rundown should anyone need it...

Acrobat 9 Pro Extended vs Pro
- Extended Version includes Adobe Presenter and Adobe LiveCycle Designer ES (beyond the scope of this article or my needs...)
- Convert to Flash Video only in Extended
- search and measurement tools for “geospatially-enabled PDF maps” only in Extended
- Convert CAD and 3D content to PDFs, again, only in Extended -- this is consistent with Photoshop CS3's (extended? basic? both?) ability to work with 3d and CAD files.

Acrobat 9 Standard
- Lacks PDF validation, redaction, and digital signatures.
- Basic stuff like form entry, plugins for Microsoft Office apps, security enabling, etc.

That brings me to the question -- Why pay US$299 for Acrobat 9 Standard when you can get ver 8 for cheaper?

General New Features in Adobe Acrobat 9 Pro
- Enable real-time collaboration of PDFs with synchronized document views and chat
- Improved Web Capture for capturing entire web pages or just some parts into PDF
- Integration with acrobat.com to enable storage and sharing of PDF files (this is kind of a big deal, as it will make the collaboration process simplier, more efficient, and easier for groups that work on projects from remote locations)
- Personalize a PDF Portfolio with customizable templates for navigation and branding (this will help with uniform PDF branding)
- Compare and highlight the differences between two versions of a PDF document
- Insert FLV (Flash) or H.264 video for direct playback in Adobe Acrobat® and Adobe Reader
- Convert a variety of video formats to FLV for playback in PDF
- Create PDF maps by importing geospatial files that retain metadata and coordinates (as a vector graphics guy who understand the viability of vector-data comprared to pixel-data, this is exciting)

Users looking to grab a free trial from Adobe.com - go here. Although there is no trial for OSX users, and from what I'm reading the only version available for OSX may be Pro (no standard, no extended).