I have Windows 8 and Adobe Acrobat Pro X, alongside CS6 Master Collection. I currently cannot open PDF documents. Every time I double-click a PDF, nothing happens. I tried double-clicking the Acrobat X icon, nothing happened. Sometimes the activity is on/off, i.e., sometimes it works, most of the times now it doesn't. This just recently started about 24 hours ago. I tried to save to PDF and I get an error such as Adobe PDF creation cannot continue because Acrobat is not activated. I fully activated my license many months ago, so I don't know why this shows up. I also just got a Fatal Error box: "Acrobat failed to connect to a DDE server." I have tried going into Task Manager and ending process on AcroTray and Adobe Acrobat Update Service. But this doesn't solve the situation. I tried downloading to the latest update 10.1.6 but that didn't fix it.
Also, yesterday, when I managed to get into Acrobat, I tried to repair installation option, that didn't fix it either.
I seem to have solved my own problem by uninstalling Acrobat fully and then re-installing it.