Upgraded iPad
UUpgraded iPad to ios8 and have lost all Pages documents
iPad, iOS 8.1
You did backup the iPad first, correct? Try restoring the backup. If you didn't, you did transfer the Pages documents to your computer first using iOS file sharing, correct? If you did, transfer them back using iOS file Sharing. If you are usingiCloud, check in iCloud.com and see if they are there. If they are not on the iPad, it's highly unlikely that they are in iCloud, but it doesn't hurt to check.
If one of those three possibilities doesn't work for you, the files are gone.