When opening MS Word or PowerPoint on a Mac, you may see the error message:

Run-time error ‘53’: 

File not found: /Library/Application Support/Adobe/MACPDFM/MacPDFM.framework/Versions/A/MacPDFM

To stop this error from coming up:

(Please keep in mind that with different versions of software the wording may change, but the steps are broadly the same)

1. Open Word or PowerPoint
2. In the Menu Bar at the top of the screen, select Tools → Templates & Add-Ins
3. Unless you have explicitly added some Templates and Plugins yourself, you should only see one item, which is the broken Add-In causing the issue
4. Select the broken Add-In and press on the minus button to remove it, which should resolve the issue. If the minus button is greyed out, proceed to the next step.
5. You should see a Full Path, i.e. where the Add-In is saved on your disk. Make a note of this path. 
6. Open a Finder window, in Menu Bar click Go → Go To Folder… (⌘⇧G) and enter the Full Path from the previous step.
7. Delete the file mentioned in the Full Path and restart the application. N.B. Be careful to not delete any other files, as you risk breaking other things.