Note: If you want to sign or hand-write on an office document for Mac, your Microsoft office version must be 2019 or 365. The other versions don’t support signing or hand-writing. 

Make sure you have the proper and latest XP-Pen driver for your tablet and that you are able to open your settings and have cursor control with your pen. 

Open Microsoft office 2019 or 365 then go to “Draw”. You should now be able to write or sign the on it.