You can transfer layered ArtRage files between the current iPad and desktop versions via iTunes file sharing.
To get the ArtRage painting file ( PTG ) from your iPad, dock your iPad, open iTunes and go to your iPads 'Apps' tab. Under 'File Sharing', click ArtRage and you'll see a listing of all your painting files which you saved to your gallery on the iPad. These can be dragged to your computer and opened in the desktop version ( File -> Open, or just double clicking the painting file )
If you're having any problems with this, let us know what desktop version you're using and how you're loading the files and we'll be happy to help.
Resident Bug-Hunter and Support Guy