Obtaining your iPad's UDID
- Open iTunes (the Mac or PC app).
- Plug in your iPad to the computer.
- Click on the iPad's name under the devices list in iTunes.
- Ensure you’re on the Summary tab.
- Click on the text that says Serial Number. It should change to say Identifier (UDID).
- Select Copy from the Edit menu.
- Your UDID is now in the clipboard, so you can paste it into an email or message.
If you don't want to mess with iTunes, there are other ways to find the UDID of your iPad -- this page provides a good set of options: