I have a lUxaire model no pbkm-ld14n100 and my central air is not very cool. What does it need?

Could be low on Freon, plugged filter, condenser fan not working. Look at the condenser fan, the one on the outside unit. Does it run when cooling is called for? Make sure all the ductwork is securly connected and that a return in the attic, if so designed, is not sucking in hot air.