and Tools -> PowerPoint Add-ins., respectively, and remove the Save as Adobe PDF add-in, by unckecking it and removing it with the '-' button and then click OK. Unfortunately that does not solve the problem for PowerPoint or Excel because if I remove SaveAsAdobePDF.ppam inside the PowerPoint folder or the SaveAsAdobePDF.xlam inside the Excel folder will trigger another error on application launch.
Go to /Users/ your-user-name-here/Library/Group Containers/UBF8T346G9.Office/User Content/Startup/Word.After looking really hard for a solution, I finally found in a very obscure page the answer, which is quite simple and works with the latest Microsoft Word on Big Sur:
