I realize this is an old thread, but I live in PA and I've bought a LOT of cars in PA and can offer my experience for future reference. And... it depends. If the car is currently titled in PA - yes - both parties generally need to be present. If the car has an out-of-state title, then only the buyer needs to be present as long as the title has been signed by the seller.
Bearing in mind - title transfer in PA is done by independent "tag shops" (often Notaries and insurance dealers as well) and each one can vary on their interpretation of the rules.
Sales tax, for example. For private party transfers that don't really have an official bill of sale, you can more or less tell them any price you want as the selling price to pay sales tax on. If the price is wildly below market value, they may raise an eyebrow, but a simple explanation ("The car need work...") is usually acceptable. Sales tax just passes through for them, so they have no incentive to collect more other than not wanting to draw attention. I'm not sure what the rules are if the car is a gift, but they may have to look up average market value and use that number. The State always wants their cut.
Most shops are not open on Sundays, so keep that in mind.
Upon titling, you generally have 30 days to get the car inspected at the independent inspection station/garage or your choice.
Side note - if you are a "car guy" looking to live in PA, it pays to develop a relationship with one station for inspections. Inspections are annual in PA, not every 2-4 years like in NJ and it generally involves two checks - one for emissions and one for safety. Emissions is pretty easy these days - anything older than 1996ish (OBD2) generally gets a visual check only. Safety involves pulling the LF & RR brakes and checking pad and rotor (or I suppose shoe & drum) condition. Then they'll check to make sure all lights and signals are working.
I've been going to the same shop for over 30 years. They know me and will often be lenient when it comes to certain inspection checks. They know I work on my own cars so if the car needs something to pass inspection, they call and ask me if I want to pay them to do it or DIY. They will put the sticker on the car no matter what as they trust me to fix the car. I usually do a quick check before taking a car to them - like brakes, and lights.
This reminds me I need to get the MINI inspected soon...