Is an employer in the state of PA legally allowed to ask an applicant on an employment application if they have a criminal history, and if so when and what? Is there specific wording that can or cannot be used.

Yep... they sure can.

Besides, many companies will run a criminal background check before hiring a candidate. By asking up front, they can ensure that the background check yields no surprises... as well as get an idea of how honest you are.

They may ask you if you have been convicted of any felony or misdemeanor

They may run criminal history reports showing all of your records.