Q: How can i cancel a pre-order in ipad itunes please ?

Perhaps you could try this to resolve your issue: http://support.apple.com/kb/HT5714

The support document listed above from Apple gives directions for canceling a pre-order from iTunes on the computer, but not from the iPad.  There must be a way to do this from the actual iPad, right?  Anyone... anyone...Bueller?

To the best of my knowledge, you can't. You can only do this through iTunes on a computer.

Regards.