Adobe X is the latest version of Adobe Acrobat and Reader software. If you still have Adobe 9 (or earlier versions) on your computer, your software is now outdated. You can get the newest version of Adobe Reader X by clicking here.
Many of the new features available in Adobe Acrobat and Reader don't apply to the average consumer. But those who work frequently with the feature in Adobe Acrobat, may find some of the new features nice. You can view a complete list of new features available in Adobe X by clicking here.