PDF is Slow to Open Preview Pane

I have adobe acrobat Pro 11 version 18 installed on my Windows 7 x64. Suddenly PDF is sporadically slow to open in Preview Pane.  I heavily rely on that to do my daily tasks. Any other files would open very quickly.  Adobe has been uninstall then reinstalled. I rolled back to previous version like 16 and 17 but none of these work. Does anyone have any suggestions on how to fix this?