You can get there from Vienna using the S-Bahn.
Once you are in the Center at the Marktplatz you can easily get to every remarkable spot by foot. The walking distances are quite short as Perchtoldsdorf is quite small.
Interesting spots in Perchtoldsdorf are the Wehrturm and the Rathaus (both 15th century) directly at the Marktplatz, and the Pfarrkirche (church from the 13th century) and Herzogsbrug (castle from the 11th century) both in 2 minuite walking distance from the Marktplatz.
Perchtoldsdorf is famous for its wine available at its Heurigen, which also serves food and local specialities for moderate prices.