One of the most useful features in Adobe Acrobat 5.0 that I used first as a student and then later even more at work was its ability to compare two documents side-by-side and mark all the differences. It is the only program I know to date that enables one to do this. I used it frequently to compare all sorts of files, usually either MS-Word documents or MS-Excel sheets. While this does involve the extra step of creating PDFs, it works beautifully in most cases.
It is the only thing that helps if you have two versions of a document created by different people and try to determine the differences so you can consolidate them into a single document. Of course, if everybody would always track their changes, that problem would arise less frequently. But there are other uses, for instance when I do not remember any more what I changed from one document to another one when I edited them some time ago.
A few months ago I finally got an upgrade to my work computer and it came with Acrobat 7.0. To my dismay I had to notice that the side-by-side comparison feature was nowhere to be found. I went to Adobe.com and tried to figure out what happened. If you go to the current Acrobat 8.0 product comparison page you are out of luck. You first have to download the detailed comparison and go down to the bottom of page 2 to find out that the feature has been removed from the Standard edition and is now only available on the Professional or 3D versions.
This is very frustrating to me, because I use many of the Standard features such as annotation, cropping, joining of documents, or removing of pages, yet have no use for the Professional features except for the side-by-side comparison. It is a real shame that that feature got “upgraded” and the Standard version downgraded. Especially because the Professional version costs 50% more.
I certainly understand the usefulness and reason for existence of the Professional version. The primary added feature seems to be that you can allow users of Acrobat Reader to edit document form fields, or allow them to annotate documents much like in the Standard version; a powerful tool for those who need it. Side-by-side comparison does not really fit into that realm of options and should have remained in the Standard edition.