If you are storing drywall for no more than a few days, you can stack it vertically against a wall. Make sure it is close enough to the wall at the bottom so the drywall does not apply too much pressure to the wall but far enough away so the stack does not tip over. Roughly 5 inches of space between the wall and drywall at the bottom should be adequate.
Where & How to Store
If the drywall will not be installed for more than a few days, it should be stacked on a flat, dry surface.
If storing drywall in a home, place stacks in the rooms where you plan to install it to reduce the amount of weight on the floor in one spot. Stack the drywall with the finished side up and ceiling drywall on the top of the stack because it will be used first.
Do not store drywall directly on a concrete floor because water will wick up through the floor and damage the drywall. If stored off the floor, drywall will need to be braced to prevent it from bowing in the middle.