Skip the line Paris

Tickets for what, exactly?

This pass allows you skip the line entry.
Nothing allows skip the line security.

http://en.parismuseumpass.com/rub-t-presentation-and-advantages-2.htm

The pass is easily purchased in Paris, at CDG Airport, participating Museums, Monuments and Paris Office of Tourism.

I suspect you are looking to book things thru "Viator"? Don't. They are a 3rd party re-seller of tickets and you can do just as well yourself with advice from the forum.

As mentioned above, which sites do you have in mind? The Paris Museum Pass, which is easy to purchase in Paris, allows you to skip the ticket buying line but NOTHING allows you to skip the security line. Some venues do have separate security lines for Museum Pass holders.

If you want to do a "skip the line" tour of the Eiffel Tower, which is not covered on the Paris Museum Pass, book directly with a provider such as Paris City Vision, not a third party. The problem with booking with a third party is that is there is a mess-up, you are on your own, because both the third party and tour operator will blame each other, denying liability. It is much easier to work only with the tour operator.

There is no such thing as a skip the line ticket; this is vendor puffery. They have exactly the same tickets you can buy on line yourself from the places you want to visit. For the Eiffel Tower, book on the official Eiffel Tower website. For museums, the museum pass can be helpful because people with tickets or passes can use a different security line; this is a big deal at the Musee d'Orsay. It is no help at all at Versailles where you can only skip the long security line with a timed entry or a King's apartment tour -- all this available from the Versailles official web site. Avoid middle men providers who sell the same stuff and add a fee.

Any ticket you purchase in advance, from a museum´s own website for example, or any pass, (such as museum or annual), will allow you to effectively skip the line.

Avoid third party vendors.