Damaged drywall is common when removing old stubborn wallpaper. It is important to repair the drywall before you begin hanging your new wallpaper. You will want to remove any loose edges with a utility knife and sand the areas with a fine-grit sandpaper. After the area is sanded and wiped clean, you can apply a primer recommended for repairing drywall. Depending on the level of damage you may need to “skim coat” your walls to smooth out imperfections after removing old wallpaper.