As shared, "system not responding" so do you get this error while opening the only pdf document or any file that you open? Also, its not clearly mentioned that which application is causing trouble for you? Is it Adobe's Acrobat or Reader?
If yes! then you may try the following steps-
1- Open the application and run the "Repair Installation". Adobe Reader>Help>Repair Installtion
2- As its system not responding error not the application not responding so you may check the "System Update" first.
3- Still no luck, then you can uninstall the app using cleaner tool- Download Adobe Reader and Acrobat Cleaner Tool - Adobe Labs and reinstall it through Adobe Acrobat Reader DC Install for all versions
Let us know if none of the solution works.