With the iTunes 10.3 (and above), it is kids-play to download anything you bought earlier, including books, songs and apps. First, make sure you are running the latest version of iTunes. If not, go to apple.com/itunes to download the latest version for your Windows or Mac. Then, start iTunes and click on the ‘purchased’ link in the “quick links” section.
After that, it will show you the list of your purchases. From here, you will see the apps and other stuff that you purchased / downloaded earlier but are not present on your iPad. Click on the ‘icloud’ button to restore stuff you bought earlier.
This new feature is something a lot of us have been asking Apple to include in iTunes. Earlier, there was no way to redownload the previously purchased app (I have never bought a song from iTunes, so I cannot say about that). But, now Apple is allowing everyone to your purchased content by clicking just few button in iTunes.
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