Museum Pass for Paris and Rome

Neither pass can be printed at home. Even if ordered online, both have to be picked up in the city, at a more limited number of locations than you can otherwise choose from when buying on the spot. It's Rome where Tabac shops/kiosks sell the Roma Pass; in Paris, the Paris Museum Pass is sold at many museums and Tourist Information offices.

I am not aware of a museum pass for Rome. When we visited they had something called a 'Romapass' which had some transport as well as a couple of free museum admissions and then discounts on other admissions i.e. a PITA to use. We bought ours from a tourist office and it did not work on the transport -- we just rode anyway but if we had been checked we would have been fined for not having a valid pass since it did not work to trigger the validation pads on the trams.

In Paris though, the Museum Pass is quite straightforward, an excellent product, and it allows you to skip the very long lines at the Orsay and the lesser lines at the Louvre and several other sites. It is easy to acquire once in Paris; I would never fiddle with trying to buy it on line and having it shipped and particularly would not buy it on line if I had to go somewhere in Paris to pick it up. Pick it up at the Cluny or even the Louvre after entering through one of the less used entrances to the museum. It is also available from the tourist office at the airport.

I bought mine on arrival at CDG in Paris this year. It was literally right in front of us when we exited the secured area of the terminal. As we walked through the airport, we saw them for sale in numerous other places. No problem to purchase on arrival and the airport is a fine place to do it. At other sites, it's a little more confusing because you have to figure out where they're sold exactly and sometimes that means working your way through a crowd and it's not always clear where to purchase.

The Paris Museum Pass does allow you to bypass the long admission lines and you can re-enter on the same day, but everyone must pass through Security lines before entering the museum or attraction. There's no avoiding the crowds unless you go very early or very late.

There's a ParisVisite Pass, which is an overpriced ripoff and should be avoided. Don't confuse them.

You should look at the official PMP website, and see if it makes sense to purchase it - both financially and if the things you want to see are included and will be open during the time limit of your pass. If you're only going to visit a couple of attractions and museums, it might not be worth buying the PMP, because you really can't do much about the crowds.
http://en.parismuseumpass.com/

It's good advice to buy the pass at the airport, or at Invalides, Cluny, or Rodin museums. Make sure to enter the date before entering the museum.

We forgot to purchase Paris Museum Passes on arrival at CDG (jet lag; baggage; ATM; SIM card; rental car; etc.), but we got them painlessly the next day at the Conciergerie (adjacent to St. Chapelle on Isle de la Cite'). No line, it's only a few minutes from Notre Dame, and our quick tour inside Conciergerie was an unscheduled treat.

While you cannot skip security with a Museum Pass you use a different and much shorter security line. This is crucial at the Orsay and helpful at the Louvre and Orangerie and several other places.

Once I bought the Paris Museum Pass at CDG. The TI's sell them (there's one in the plaza at Notre Dame). The last time I bought one was at Les Printemps (or maybe it was Galeries Lafayette next door) department store.

The one time I bought the Romapass, it was only worth it because I was going to the most expensive sights, including the Borghese. If you want to visit the Borghese, you must book well in advance. When I did it, several years ago, you couldn't book online with the pass, you had to call - or have your hotel do it. If you want to avoid the long lines at the Vatican Museums, you should get timed entry tickets online (there's a separate security line for reservations) or book a tour.