Hi,
Based on my knowledge, the option is document-based, we can't control this on the Policy level.
If your request is to turn on this option for all new created documents. Since all new documents are based on the Normal.dotm template, a workaround is to create a new Normal.dotm template in which this option is checked:
Browse to C:\Users\Username\AppData\Roaming\Microsoft\Templates, open Normal.dotm, tick the option and save it as Normal_1.dotm, save it in the same location.
Then rename the old Normal.dotm to Normal.old, rename Normal_1.dotm to Normal.dotm.
Open Word and create a new blank document, you will see this option is ticked.
To deploy this file for all users, we can write a startup script. The process is like: 1. Remove the old Normal.dotm, 2. Copy the new Normal.dotm template from a network shared location to C:\Users\Username\AppData\Roaming\Microsoft\Templates.
I hope the information is helpful to you.
Regards,
Melon Chen
TechNet Community Su