For me, Fedora 39 (testing on this atm), evince gave me a full PDF view in presentation mode, however it was rather small. On a whim, installed Okular (KDE application, but running it on GNOME).
Okular presented full size and I suspect, will perform better with automatic sizing on Wayland. It’s extra Qt libraries (dependencies), but give this a try.
Strange enough only in full-screen mode, not in in presentation mode: In presentation mode there is a thin, noisy, distorted thing at the right hand side.
I’ve had a couple of what I think are related bugs involving FSR in proton and xrandr/monitor management and scaling in plasma which I think is due to various tools not supporting the 3:2 native aspect of the panel.
These bugs likely need to be filed with the upstream project trackers as I don’t think they are framework specific.