Are you absolutely sure it doesn't have a slide switch on the bottom of the fan near where the pull chains come out? I'm assuming it is a home type fan with a pull chain switch on it, (even if you don't use the pull chain sw, it may be there w/short chain on it.)
If you have a commercial/industrial fan that doesn't have pull switches on the bottom, such as
the Home Depot Industrial ceiling fans in this thread, then you may find the reversing switch on top of the unit. find the "bell" cover on top and loosen the set screw holding it and slide it up the down-
rod. Under this cover, you will find a reversing switch.
That being said, reversing ceiling fans probably has some effect in a low ceiling room in a house with no obstructions to air flow along the walls. For a garage or shop, especially one with no ceiling or lots of stuff around the walls, or a tall ceiling, it probably is a waste to bother reversing them.
Charles