Finally fixed it. Running it in commandline revealed the same issue of "Unhandled Exception: System.UnauthorizedAccessException: Access to the path 'C:\WINDOWS\system32\spool\DRIVERS\x64\PS_SCHM.GDL' is denied."
So I just enabled all permissions for that file. First you have to make yourself the "Owner" : Right Click, Properties, Security tab, "Advanced" button", at the top there is "Owner:", click "Change" to the right of that, find your user and set it. Then press OK all the way out. Come back into Properties/Security, Edit permissions, give everyone full control. Then reinstall the printer (commandline or GUI attempt from PDFCreator).