I'm not sure what you mean by "automatically added to the Apple iCloud." You would have to have turned on the iCloud Drive option on your MacBook Pro and then opted to save the file to iCloud Drive, or you would have had to turn on the Desktop and Documents option for iCloud Drive and then saved the file to anywhere in Desktop and Documents.
Once a file is saved to iCloud Drive you can edit it from an iPad 4.
The following from Microsoft Word on the App Store explains the relationship to Office 365 (you can edit documents on an iPad with a screen size of 10.1 inches or smaller without an Office 365 subscription).
To create or edit documents, sign in with a free Microsoft account on devices with a screen size of 10.1 inches or smaller.
Unlock the full Microsoft Office experience with a qualifying Office 365 subscription (see http://aka.ms/Office365subscriptions) for your phone, tablet, PC and Mac.
If you do have an Office 365 subscription, it includes free storage on OneDrive and you may find that more convenient to use with Microsoft products than iCloud Drive, but both will work.