Well, this is interesting (and encouraging!). I created a new note and inserted two PDF’s from ones I created from Internet articles. They render perfectly. Hmmm, I wonder what is unique about the one that will not render?
My apologies, I certainly did not mean to “cry wolf.”
Here is a screenshot of the test note.
I then added the problematic PDF to that same note. It sill does not render. This tells me there is something peculiar about that PDF.