(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".)
Cams: Leica, Sony, Canon, Nikon, Sigma, Fuji, Panasonic and Pentax... mainly.
Lenses: Voigtländer, Leica, Sony, Sigma, Nikkor, Tokina, Tamron and some others.