Things are now working. I opened Help, went to repair instillation. That did not fix the problem. I then went to Check for updates. It came back that no updates are available but opening a previously unprintable PDF file now prints. This has only occupied about 6 hours of my time including several of lost sleep in the process. Not a happy camper about that but at least I can once again print PDF files. Perhaps my floundering approach may help someone else.