We are running a 600+ iPad 1:1 program and also deploy hundreds of OS X devices. Every single year, we struggle with file compatibility between iOS and OS X. We tested the iOS 8 file compatibility with OS X Mavericks when it was released, but then Apple released another update of iOS iWork apps on the same day as Yosemite was released.
Since we can't jump on the updatewagon on our OS X devices, but we did eventually upgrade to iOS 8, we now have issues because noone with OS X Mavericks can't open an iWork document that was created on iWork for iOS 8.
How do you ensure compatibility?