As the title says I found a particular pdf in wich okular's review function is not working. Whenever I press F the review menu doesn't show, and by trying to access it via tools -> menu it looks like the function is disabled. Why does this happen in a particular pdf (all other pdfs I've read in okular didn't have this problem).
I believe that there are PDF's that have flags that set them as readonly. Use
This uses Ghostscript to print the PDF into Postscript and then back into PDF, thus circumventing the readonly mechanism.