(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: Leica, Fuji, Nikon, Pentax, Canon
Main Lenses: Voigtländer, Leica, Fuji, Nikkor, Pentax, Sigma