To completely delete personal information and data from an iPad, you must wipe the device. IPads can be wiped directly from the Settings application or by connecting the device to iTunes on a computer.
Wiping an iPad From the Settings App
In Settings, select General. Scroll to the bottom of the screen and select Reset. Select Erase All Content and Settings and then click Erase twice in the dialog boxes to wipe the iPad. The iPad displays an Apple logo loading screen while wiping and returns to the initial iPad setup screen when the process is complete.
Wiping an iPad via iTunes on a Computer
Connect the iPad to the computer using the USB charging cord and open iTunes. Click Trust in the dialog box that appears on the iPad. Click on the iPad icon near the top left of the iTunes window to access the Summary screen. Click Restore iPad and then Check in the automatic updates dialog box. Finally, click Restore and Update to wipe the device and update it to the latest iOS version. Make sure to leave the iPad connected to the computer and iTunes open while the device restores. A restore confirmation dialog box appears when the process is complete.