PREVIEW NOT SAVING KEYWORDS - Catalina OS

Ever since I upgraded to Catalina, my keywords are not saving in Preview. It looks like they will, but when I go back to open the pdf, they are not there. I contacted Apple and they also had the same problem. The tech seemed surprised. I guess not many folks have called and complained. I depend on keywords to easily find documents with similar themes. Apple said they didn't know when it would be fixed! Nuts! It was working fine before. When I asked them for an alternative they said to try Acrobat. I don't want to spend that much money just to add keywords to pdfs. The free version won't allow me to add keywords and I don't want to spend $50+ to add keywords. Any suggestions out there either for a work around or a free or inexpensive pdf editor that will allow me to add keywords?