Currently, there’s really no way to do that without using scripting to leverage the “shell” function to get your machine to run a PDF viewer, say. And the details differ depending on whether you’re on a PC or a Mac.
Having said that, most people tend to do this the other way around. For example, some people use an iPad to run a setlist sheet music manager (such as forScore) which can send out program changes to Gig Performer when you select your song. That’s how I do it. Setlist manager and its big brother, Band Helper are other examples.
There are also several sheet music setlist programs that run directly on Macs and PCs and they can generally send out program changes as well.
My own approach is to drive Gig Performer directly while developing sounds/rackspaces and so forth but when I’m on stage, it essentially becomes a “server” controlled from keyboards or guitar pedal boards or by a separately running set list manager or even via OSC for remote control and I never go near the laptop.
Other users might have other thoughts.