The closest international airports are Venice Marco Polo (http://www.veniceairport.it/), Treviso Antonio Canova (http://www.trevisoairport.it) and Verona Valerio Catullo (http://www.aeroportoverona.it/). From there you can easily reach Padua by means of bus or taxi.
If you wish to take a taxi, Airservice provides a very convenient shared shuttle van service. It has to be booked at least 24 hours before your arrival/departure with the reservation form you find on the web-site http://www.airservicepadova.it/, or calling the +39 049 8744025; e-mail: firstname.lastname@example.org. The Airservice will cost about 25,00 Euros per person and the journey is about 40 minutes long. Please notice that if you do not reserve the Airservice, a taxi will cost you at least 3 or 4 times more. Payment is directly due to the driver who will give you back a receipt, by cash or credit card (VISA only). For a normal taxi transfer, consider the following options: Cooperativa Radio Taxi Padova (http://www.taxipadova.it/, tel. +39 049 651333), or Landomas Service (http://www.landomas.it/, tel. +39 049 8601426).
From Venice and Treviso, you can also take a bus, that will cost you about 4 €. SITA Buses to Padua are right outside the arrivals lounge and leave from the airport every half an hour. You can buy tickets on board or in the arrivals lounge at the ATVO/ACTT ticket office from 8 am to 11 pm. Schedule on http://ro.autobus.it/ro/asp/RicercaOrari.asp?User=SITA.
If you are coming by car, take the A4 motorway (Milano-Venezia) and exit at Padova Est gate if arriving from Venice, or Padova Ovest if arriving from Milan. In case you are driving the A13 motorway (Bologna-Padova), take Padova Sud gate. More information at http://www.autostrade.it or http://www.viamichelin.com for a detailed trip plan. A not exclusive list of parking areas can be found at the following website http://www.parcheggipadova.it/.
Padova is also reached by international high-speed trains. Schedule on http://www.trenitalia.com.