How did you turn it on, via Settings or a triple-click of the home button ? You could try triple-clicking the home button and see if that turns it off, and if it does you can then change what a triple-click does via Settings > General > Accessibility > Triple-Click Home.
If that doesn't turn it off then you can either turn it off directly on the iPad (you need to use a tap-to-select and then double-tap to activate/type process and 3 fingered scrolling ; so to type a digit of the passcode tap the digit so that it gets a box around it and then double-tap it to type it) to go into Settings > General > Accessibility and turn VoiceOver 'off', or you can do it by connecting to your computer's iTunes : http://support.apple.com/kb/HT4064