The situation:
I'm getting a "Missing Required Windows Service: Please ensure that required 'TabletInputService' is running" warning and cannot start PDF Annotator.
The solution:
"TabletInputService" is part of the Windows operating system, and required to run PDF Annotator.
To start this service, and to configure it so that it automatically starts with Windows, please follow these steps:
services.msc
and hit ENTER.