I am installing a new shower pan since there weren't any in my house built in 1985. I was reading various literature and it says before I put in my sloped concrete I need to put down a liner of roofing felt. Do I need to do that over concrete subfloor or just a wooden subfloor? Please help.

I am not sure,but here is my 2 cents worth.
Felt paper will stop moisture from full contact between the concrete and your new pan,mainly the purpose of felt in roofing is for moisture diversion,condensation barrier,etc.

The heat from hot water in a shower base and concrete flooring will cause condensation so it does make sense to put it down,just my opinion,

Ken