We are a group of 5 persons travelling to Paris in a couple of weeks. I am wondering if we can buy a carnet of 10 tickets and use it both ways, from CDG to Paris as well as from Paris to CDG. And the same thing travelling to Versailles. It would be less expensive but is the direction printed on the ticket decisive?
Yes you can split a carnet/book of train tickets any way you wish. Direction is not printed on the Paris city train tickets (RER, Transilien, Metro tickets), just the overall journey and can be used in either direction.