Technically, there are no presidential candidates on the ballot in Pennsylvania's primary ... only delegates. The presidential candidate affiliation of delegates isn't even displayed on the ballot. A voter is expected to know who represents whom before arriving at his/her polling station.
So, please learn who your Ron Paul delegate (and alternate delegate) candidates are. You can find them here:
http://www.ronpaulpa.com/congressional_districts.php
If you don't know your district, in another thread MMalloy provided the following link to find it:
http://www.govtrack.us/congress/findyourreps.xpd