I assume you mean Padova?
As Sam mentioned, a rail pass would definitely not be cost effective! Keep in mind that if using the fast trains, these have compulsory seat reservations which are NOT included with rail passes. You'd have to pay separately out-of-pocket for those.
I'd suggest using Regionale trains as much as possible, and particularly the Regionale Veloce as they're about as quick as the fast trains (for much less money). Current fares are listed at €4.15 PP each way. You can see all the solutions on the Trenitalia website.
One important point to add is that with locally purchased Regionale tickets, you *must** validate these prior to boarding the train on the day of travel or risk hefty fines, which will be collected on the spot! DON'T forget, as the fine is about €50 PP! The same applies to Vaporetto tickets in Venice (in that case, the validation machine is electronic - if you get a green light, you're good to go).