I've never played with rudder trim on any of the PA-28's I've flown. I probably should when using ones with an autopilot, as that's apparently the thing to do to have it flying straight. But that said, I've never noticed having to use any significant rudder in cruise on any of them, nor having the aircraft try to drift left or right when taxiing. And that's on maybe 8-10 different PA-28s flown? Maybe I'm just heavy on my feet and don't notice it. But maybe your aircraft is a little bit out of being rigged straight? That's a complete guess...but maybe worth flying/renting another PA-28 that is known to fly straight and see if yours is distinctly different? Again...a guess. I can fly the things, more or less, but tuning them up is NOT one of my skill sets.