I need to card Navigo decouverte and to activate weekly Navigo pass. Where can I buy it in CGD upon arrival?
Navigo Decouverte card / Navigo Pass can be purchased from the CDG airport train station ticket counters at CDG Terminal 2 train station and CDG Terminal 1 / Roissypole train station. Those links have photo instructions of how to get to the train station and what the ticket counters look like at both CDG Airport train stations.
Note that ticket vending machines at these CDG Airport train stations can refill / add Navigo pass onto cards, but you cannot buy blank/new cards from these ticket vending machines. If you do not already have a Navigo card, you must purchase that first from a ticket window.