If you are using it to set up the sights on a pistol (or something like a 9mm carbine such as Hi-Point's 995TS), you need to remember that even at 7 to 25 yards (most indoor target ranges) there will be some drop of the bullet. If you set the sights to exactly align with the laser's point of impact at the target range, your bullets will hit the target low with the amount dependent on distance (less than 0.5" at 7 yds, but a little more than 2" at 25 yds if memory serves correctly).
I use mine to check the approximate sight alignment after any work involving the slide or barrel. This keeps me close. I also used it for an initial sighting in when I added a 3-9X42 scope to the 999TS carbine. (Only took about 4 bullets down range to get the scope close enough for plinking at the range.)
The same thing will apply if you add a laser (such as Crimson Trace) to your pistol. However, for self-defense range shooting, this will get you very close to the desired target area. At typical SD distances, you will be off only by about 0.5" or less.
According to this trajectory table, a 115gr. 9mm, fired from a 4" bbl, will have less than a 1" drop at 25 yards. At self defense ranges, this would be far less and well within the "margin of error" for high stress shooting.
Yes, the PF-9 has a 1" shorter bbl which will translate into lower velocity and more bullet drop. Still negligible at SD ranges.