Let me preface this that I know very little about iPads.
A client of mine has several iPads that they use for business and are using DropBox on them.
They want to save the data in the DropBox to the Windows 2012 R2 server that is running AD.
To me it would be smartest to setup a couple of Windows PCs that are part of the domain with the DropBox accounts then have the data on those PCs be on one of the mapped drives of the file server.
Is their an easier way than this to do it from the iPads without opening up the AD to everyone?