Preview: cannot paste

My question is about copying and pasting elsewhere a detail in a pdf on my Mac (Mojave).

I have a pdf of a musical score, originally typeset in Finale. The Finale score was unfortunately deleted. An isolated 'f' notation is missing from a particular passage in this pdf, and I wish to copy an identical notation from elsewhere in the score and paste it where it at present is missing.

If I open the pdf in Preview, I can copy the 'f' from where it is present, but I cannot find a way of pasting it in the location from which it is missing. I shoud be grateful for advice about how to paste in Preview.