When you visit the IRS Where to File Paper Tax Returns webpage and choose the "Pennsylvania" link, it indicates that you should send a return for which you are not enclosing a payment to:
Department of the Treasury
Internal Revenue Service
Ogden, UT 84201-xxxx , where xxxx = 0002 (Form 1040), 0015 (Form 1040A), or 0014 (Form 1040-EZ)