I have pressed a few in myself with a 6 ton press. They were only 305 pistons so no big deal if i messed up. A few were tight afterwards but my machinist said as long as you can move them by hand it will be ok. Like stated above I wouldn't advise doing it yourself. I always run float pins if i have the choice.
Machine shops have a special fixture to hold the rod and piston so all the force is exerted on the rod and not the piston. The idea is the pin spins freely in the piston pin bores but is tight on the small end of the rod. So when you press the pin into the rod you want to be pressing against the rod not the side of the piston(if that makes any sense).
If they are stock cast pistons with stock rods that will be in a low rpm beater sure whatever try it, but anything mildly performance oriented spend the extra money to have the machinist do it. They will know what feels like a good fit or if its taking too much force.
Like cobalt said some places heat up the small end of the rod so it expands then it can be easily slid into position.