Looking on the SNCF website for your dates, I don't see any direct trains from Caen to Paris. They all require changes. Perhaps they're doing work on the line?
A 17 minute transfer is not tight in a smaller station like Le Mans, unless you have some reason for reduced mobility (heavy bags, traveling with small children, slow walker, etc). Even then, it should be fine. Looking at Le Mans station on Google Maps, it appears that it only has 4 platforms, and that there are elevators. So, you arrive on a platform, take the elevator down to the passageway connecting the platforms, then find your next platform and take the elevator up to it. That is, if our arrival and departure platforms are not across from each other; then no elevator is needed. Of course, there are stairs as well.