Hello,
I've just used the rM to annotate a landscape PDF (size 453.54 x 255.12 pts), and exportNotebook does not handle the case at all.
I've tried to hack it into supporting it but for some reason I can't get the translate to work.
However, I've stumbled upon https://github.com/tavinus/pdfScale/ which seems to have everything we need (almost, I could not get the automatic translate to work).
I'll see if I manage to do something, but don't count on it :)