You might be confusing an iTunes account with an iCloud account.
Multiple users can use the same iTunes account on their devices and thus share purchased music, apps, etc. and each have different iCloud accounts (using a different Apple ID) in order to keep email, contacts, calendars, etc. separate. On a single device, you can enter an ID for the iTunes store and a different ID for iCloud.
But if they all have different iCloud accounts, they can share some calendars and reminders, but everything else is separate. Thus notes cannot be shared.
Thanks - that makes sense.
Im trying to tidy this up and mnake it easier to move between the different accounts - I'd like to rename my Apple ID after my icloud mail address, rather than my hotmail (which I want to stop using). However despite a few attempts Ive been unable to change my Apple ID to my iCloud address - do you know why?
To manage the Apple ID:
If you need to change the password, under the Manage your Apple ID section on the right, click the link to Change your password.
To change to a different, existing, icloud account on a device:
Settings>iCloud, scroll to bottom of page and tap Delete Account. This disconnects the account from the device, it does not delete data. Then log in with the other ID.
See this for more tips: