Originally posted by Surry but apart from that will any mounting related problem appear?
All K mount equipment is interchangeable and performs within the limits of the lowest common denominator. So a Kaf lens will mount just fine but will only perform with the features available to both pieces of equipment. In this case, all manual, no auto focus, etc.
You do have to watch out for lenses that do not have an aperture ring. DA lenses and FA J lenses I believe. These will still mount properly but without an aperture ring there is no way to control the aperture and thus you shoot wide open all the time.
Here is a compatibility chart that might help:
http://www.mosphotos.com/PentaxLensCompatibility.html