I have been using Okular (1.3.3) on Ubuntu (18.04) for a while now and feel pretty confident in my ability to be productive in it. However, suddenly, I am lost.
I opened a PDF (as I have done 100s of times) and pressed F6 to get the annotations toolbar. Nothing happened. I checked for stuck keys on my keyboard. Nothing changed. I closed the PDF and opened another PDF and everything works as expected. I went back and opened the troublesome PDF.
Under the Tools menu, Review (F6) is grayed out (disabled). I checked the file to see if it was read-only. It was not.
Any ideas why the annotation toolbar would not be available in some PDF but would in others? Any idea how to fix it?