Originally Posted by Mono
If I understand you well, you try to annotate scanned pdf. It is not possible (there is no text to be anotated, just picture of text)...
Someone suggested to use OCR and add "text layer" to scanned pdf. I newer tried it, so I do not know whether and how it works on M92. (It is not possible to do OCR on M92, you have to do it on PC.)