I've been having this issue the last month or so. I reset the data counters to check this and "Documents and Sync" used 2.5GB in 2 days. This is really out of hand. I burned through 20GB on my phone last month. Thankfully my telco was understanding and removed any overage charges. Still, this needs to be fixed.
A bunch of these were recommended in another thread and I tried them all:
- Removing the "Pages" app
- Removing keyboard shortcuts
- Turning off hand-off
- Turning off all sync except for Find My Iphone, Contacts, Notes and Photos
Just then I logged out of iCloud, created a new iCloud account and logged back in. I've only turned on "Find my iPhone". Will report back on how I go.