Throw iTunes you can transfer the books to your iPad.
1.Download the ereader that supports Adobe Reader Mobile SDK (DL reader or Bluefire) reader oniPad
2.Go to Apps tab in iTunes
3.Scroll below the File Sharing
4.Select the ereader fromm the list
5.Click on Add button in right side and select the epub file
(ADE files you have downloaded will be there in "My Digital Editions" folder)
Video tutorial: http://www.youtube.com/watch?v=7kpyOU9WJo0#t=279