When you note "Three Versions of OS X" - were these in-place upgrades? In-place upgrades are notoriously flaky and clean installations are recommended. (You will not see any documentation from either Microsoft or Apple to this, but it is pretty well known fact.)
Have you tried creating another user account and testing?
Nope. Clean OS installs.
Three different computers, too. Should have mentioned that. It has always worked this way for me: If a document is currently open in Acrobat Pro on the Mac, I cannot double-click another PDF document and load it for editing. Is this really not happening to everyone? It has been consistent across computers, versions of Mac OS X, and versions of Acrobat Pro for years. Thanks. -- Ken
I just double checked and I opened Acrobat XI first then did ⌘-H to hide Acrobat. Then I located a PDF and Double Clicked.
I've never had your issue since OSX.2.8 up to OSX.9.0 (Mavericks). So it’s a problem with your set up or some type of Utilitity , Plugin or extension is interfering.
I don't know how to tell you how to troubleshoot.
Try the Following:
Restart with shift key down
Then open acrobat.
Then Hide Acrobat and double click on a PDF.
If you don't have the problem you have a a Startup Item.
Will investigate other startup items, but the important part is a PDF has to be open in Acrobat Pro to cause the failure. If Acrobat is open and hidden, there's no problem.
And now, it's not reproducible, 'cause I just tried it and it worked fine. (Quit Acrobat. Double-clicked a PDF to load it, and then double-clicked a second one. They both loaded fine.) But it happens often, and clearly, I'm not the only one (search on the exact words of the error message, and you'll find a lot of hits).
But I'll try starting up with no other apps loaded, and see what happens.