Save program from iPad to Mac
You can log into your iTunes Store account in iTunes on the Mac and download the app there. As long as you have a copy on your Mac you can always sync it to your iPad if required.

The .ipa file (the app) is stored in /Users/&lt;youruser&gt;/Music/iTunes/iTunes Media/Mobile Applications, the name may need some guessing. You can also right-click on the app icon directly in the App view in iTunes and select "Show in Finder"