I have resolved the issue with Acrobat freezing in MacOS. This also works with Reader freezing.
- Open Acrobat/Reader click on the user's account in the top right corner and sign the user out. The program will freeze after this. Force Quit the App.
- Open Acrobat/Reader again.
- A sign-in box should appear.
- Go through the sign-in process and the app should now go on working as normal.
- Click on the user's account in the top right corner, and select "Preferences"
- Click on "Adobe Online Services"
- Unselect "Sync Preferences across devices and document services"
- Click "Ok" and now Acrobat/Reader shouldn't freeze again.