Hello Einarl,
I am sorry for the trouble you had, please reboot the machine once and locate Adobe Reader's icon, right-click and select Run as Administrator and check.
If you are able to launch Adobe Reader, try repairing the installation files from help menu of Adobe Reader>Repair installation, reboot the machine. Then check for any pending updates of Adobe Reader from help>check for updates, install the updates and reboot the machine.
Also, check for any pending updates of Windows from Control Panel, install the updates and reboot the machine, Then try launching Adobe Reader and check.
If you are not able to launch Adobe Reader at all, please use Acrobat cleaner tool to remove the currently installed Adobe Reader Download Adobe Reader and Acrobat Cleaner Tool - Adobe Labs
Reboot the machine and install Adobe Reader from Adobe - Adobe Acrobat Reader DC Distribution
Once Adobe Reader is installed, navigate to C:\Program Files (x86)\Adobe\Acrobat Reader DC\Reader
Now find and double-click to open the Eula.exe application.

Accept the license agreement. Relaunch the application and try to open a PDF file and check.
Let us know how it goes and share your observation.
Thanks,
Anand Sri.