Inkbook Prime - syncing with Moon Reader

Is there any way to sync Moon Reader across devices with Inkbook Prime? I have tried and failed, since:

• It is impossible to install Google Drive for syncing as the Inkbook does not support google accounts
• Android 4.2.2, which Inkbook Prime runs, is not compatible with the DropBox v2 API. So page syncing is not possible.

Maybe I am missing something obvious. Otherwise, is rooting the only way to get any of these cloud syncing apps to work? Thanks...