I work on an iMac. It seemed that "suddenly" InDesign would not export my document as a PDF!@$#!!
I've never had this issue until today. YESTERDAY I was messing with my SECURITY & PRIVACY PREFS in the OS.
I had UNCHECKED Full Disk Access for InDesign. THAT'S WHAT MESSED THINGS UP.
FULL DISK ACCESS must be allowed for InDesign to find all the links and art in the file you're working on, as it CREATES THE PDF.
Sure enough, I went back into prefs and GAVE INDESIGN FULL DISK ACCESS and it's working fine.
Hope this helps those in need ;-)).