How do I upgrade my iPad 3 from iOS 5.1 to 7.x (now when the latest version is >8)?
- First backup your iPad in case something goes wrong (if you have jailbroken your device I advice you to save your shsh blobs, it's not necessary).
- Next download the os version you want to upgrade to from https://ipsw.me/
- Finally open iTunes, cancel if asked for an update. Go to your iPad's summary page. Hold alt/option key (OS X), or Shift key (Windows) and click on restore. A window will show up choose the ipsw your downloaded before and and your upgrade will start. Then afterwards reinstall the backup.