That depends on the printer.
Laser printers are usually center-aligned, while inkjets are almost always edge-aligned.
The way to tell is look at the printer... if BOTH paper guides move towards the center on the manual input, then it's center aligned. If only one moves, then it's edge aligned.
Just my 2¢
"In order to start solving a problem, one must first identify its owner." --Me
--Greg