I've seen this more and more on my machines since version 10.1.3. Found a fix here:
..but the one registry value listed there is wrong (bDontShowMsgWhenViewingDoc should be set to "1"). I tested on a couple of machines with the issue and the moment these settings were in place, Adobe Reader behaved normally (with processes closing out completely instead of hanging and sometimes spiking the CPU).
For anyone else who has run into this issue and wants to deploy the fix using a K1000 script, here's the registry keys that need added:
Windows Registry Editor Version 5.00
And my script settings:
Hope that helps!