How to update an app by ad hoc distribution

I have developed an 开发者_如何学PythoniPad app and distributed it via ad hoc means. Now I need to send out an updated version. However it seems the ad hoc method won't replace the app currently on the iPad, I can only see the new version on the iPad if I delete the current one and sync after that. I want to avoid deleting the current one as through its normal use it has built up a folder of images that is annoying to replace.

Is it possible to UPDATE an app using ad hoc distribution without having to DELETE the current one from the iPad first?

Thanks, Steve

Maybe the problem is your new app doesn't actually have a higher version number.

Yes, I use ad-hoc distribution and update all the time.