Can’t edit word documents

Try restarting the computer. Make sure to uncheck "Reopen windows" from the pop-up window that appears when restarting so that all of your apps close and will need to be relaunched.

Try booting into Safe Mode to see if you can edit the document. If this works, then it usually means you have an issue with some third party software which is interfering with the normal operation of macOS. Typical culprits are anti-virus apps, cleaning apps, and third party security software. If you have any of these types of apps installed, then uninstall them by following the developer's instructions since these types of apps are not needed on a Mac and they usually cause more problems than they solve, plus they impact system performance.

If you are using Microsoft Office, make sure it is not in demo mode. Even if you have a valid license, there is a possibility something may have happened to your activation of Office. Usually there will be a notification bar at the top of the app window with the notice to activate the product, but if you go to "File --> New" to create a new document which will alert you to problem as well.

If this is not the issue, then where is the file located that you are trying to edit? Can you use the Finder to create a folder at the same location? Check the permissions on the file you are trying to edit.

What is the exact model of your Mac as well as the version of macOS being used? You can get this information by clicking the Apple menu and selecting "About This Mac".