Can I buy a 5 day Paris Visite Pass (65.80 Euro) on the internet? If not, can I purchase it at CDG?
There are links for online purchases of Paris Visite at the bottom of the linked article. Note that there will be a substantial handling / delivery fee.
Paris Visite Passes at CDG Airport are sold at both CDG Terminal 1 train station and CDG Terminal 2 train station.