(I'm not sure if this is the right category, but I thought this post would fit best here...)
There you can find a nice collection of RF manuals.
(Despite the website's name, not "Pentax".)
Main Cams: Fuji, Leica, Nikon, Pentax, Panasonic, Canon
Main Lenses: Fuji, Voigtländer, Leica, Nikkor, Pentax, Sigma etc.