Laura, you did not state how old your house is, or if the pocket door is a single or double door. If the house was built prior to the forties, and the doors are double doors, (that is, they meet in the middle), the doors likely have adjustable wheels that run in the track. Even if it's a single door, this may be true. Try pulling the door out of the wall, then stand on a ladder or stool, (make sure it's stable), and look at the top of the door and the track it runs on. You may need a flashlight. If there is a bolt, or a screw in front of, or beside the wheel, this could be an adjust for the height. If you screw it tighter, it should raise the door and lower it if unscrewed. If there are only the wheels, then you will likely have to follow Don's advise. Good luck.