Q: Pages, keynote, numbers not free on iPad Air

The download of those apps is associated with the original ID used. You have to sign in with that original ID to get a copy of those apps redownloaded to your iPad.

How to get all the iWork apps, iPhoto, and iMovie for free on an eligible iPhone or iPad

http://www.imore.com/how-get-all-iwork-apps-iphoto-and-imovie-free-eligible-ipho ne-or-ipad

About Free Apple Apps for iOS 7 compatible devices

http://support.apple.com/kb/HT5913

Downloading Past Purchases from the iTunes Store, App Store and iBooks Store

http://support.apple.com/kb/ht2519

 Cheers, Tom

It's a mistake to change the Apple ID; it will no longer be free.

You must use the Apple ID that you use to activate iPad.