The surface is textured so that the parts stick better. If you want a smooth surface, it should be fine to turn it upside down. But you will be a little more likely to have prints come off the bed.
I have printed on the smooth side. At first the prints stuck well. Then the border started releasing. I tried brim but that did not help. Tried a glue stick which worked but it took away from the smooth finish. Tried a very light coating of hairspray and it worked well.