The issue is one that i have tested on multiple machines. On computers where Acrobat Reader DC is the PDF viewer for WinOMS it's causing WinOMS to freeze up, a lot of times it's when the preview window displays, then you try to move to another area of WinOMS. It just sits there thinking then finally will go to the next screen. On computers that have Acrobat 9 Standard (it's an old version i know but it's what they have) there is no problem when it's the default PDF viewer for WinOMS. No freezes ups, Hiccups, works as normal. I have seen this at two different practices. It happens whether it's Windows 7, 8.1 or Windows 10. I eliminated as many variables as possible and it's the same result (Security, Application Conflicts, Networking etc). I have looked through settings in Acrobat DC thinking maybe it was some sort of security option or whatnot and nothing fixes the problem other than to uninstall Acrobat Reader DC and install Acrobat 9 Standard. I don't know if 10, 11 version of Reader or Standard/Pro would work or not. I can download the older reader but you have to purchase a newer version of Acrobat Standard/Pro. Still on WinOMS 9.1 so not sure if going to 9.2 will help or not.