ARD is not a conviction so if an application asks for any convictions you have that would certainly not be one of them. I would reccomend that you contact an employment attorney for your question regarding what an employer can and cannot do. I do know that many applications are now asking for prior records including any alternative programs a person may have been a part of such as ARD. Again this may be somethig you would want to discuss with an employment attorney which I recommend you do.
If the job application asks about CONVICTIONS, then no, you weren't convicted and may truthfully answer as such. If the application asks a broader question ("Have you ever been charged...") then answer truthfully (typically, only government jobs, or jobs that require security clearance will ask about charges that did not result in conviction).
However, since Pennsylvania is a pro-employer at-will state, any ARD that has not yet been expunged will appear on a background check, and the employer can simply decide not to hire you.
I agree with my colleagues. If they only ask about convictions, then I would not put arrests that do not lead to conviction. ARD is not a conviction. The record of the arrest should be expunged so you do not need to address this in the future.
It should also be noted that PA is an "at-will" employment state, meaning that they do not really need any reason at all to terminate employment (unless you can prove it was based upon race, religion etc.).
Michael L. Doyle
Attorney at Will