Just one clarification. Since you are arriving from Italy (a Schengen country) airside transfer is not possible. 2D and 2F1 are the two Schengen terminals at CDG2 and they do not have stops for the airside bus. As mentioned above, it's like a domestic flight and that means you will have to walk or take the landside bus (and there are quite a few different ones, so this can be quite tricky). The best (and really the only easy) way to do this is walk from 2F1 to 2A (about 10-15 minutes) and then clear passport control and security in 2A. Your luggage should be checked through and you should be able to get your boarding pass for the CO flight in Venice. But if you need an additional stop at a transfer desk (or at CO check-in) in CDG to get your CO boarding pass you will most likely miss your flight. Personally, I think you should call CO and see if you can switch to the 11:25 flight. If CO says "no," then be mentally prepared to try to go standby on CO or AF later that day.