I’ve been using the new PDF viewer the past few days and wanted to add another suggestion: at the moment, notes display what page they’re on within the PDF (p. 1, 2, 3 etc.) but these rarely match up with the actual page numbers in the document itself (which is usually from a journal several hundred pages long). This means that I have to refer back to the PDF to check what page a note is referencing if I export it, and in order to cite it properly.
It would be really useful if you could tell the PDF viewer somehow what page numbers in the document the pages of the PDF match up to - e.g. tell it that page 1 of the PDF is actually page 125 of the paper itself. Notes could then display the actual page number they relate to rather than just the page of the PDF document they’re on (which is a bit useless in and of itself).
This would make exported notes a lot more useful once they were exported as you could just use them directly for referencing without having to refer back to the original PDF to check what actual page number each relates to.