Do I pay Maryland taxes if I live in PA and my job is located in Maryland

It depends.

If you live AND work in PA, you pay ONLY PA Taxes.

If live in PA, but work in MD, you pay only MD taxes, because you will get a tax credit for MD taxes on the PA tax return that will cover your PA tax liability.

Actually MD and PA have reciprocal tax agreements, so your employer can deduct PA taxes from your pay instead of MD taxes even though you work in MD. This makes it easier for you, as you then only have to file a PA resident tax return and no MD tax return is required. To do this submit form MW507 to your employer: http://forms.marylandtaxes.com/current_forms/mw507.pdf