Upvote:3
Hi I went through CDG recently and my boarding pass was checked for final destination by airport stuff before they allowed me to take the tunnel between terminals 2F and 2E.
I would say you are only allowed on your departure terminal.
Also according to http://easycdg.com/passenger-information/connecting-flight-connections-paris-cdg-airport/transfer-terminal-2e/
It takes 45 minutes to go from 2E to 2D and you need to pass through security so even if they allow you on 2D you’ll spend huge amount of time walking and passing the security check.
Please note due to recent events security is tightened so there are document and boarding pass checks at every opportunity and they are more strict than usual so they take even more time.