If you've decided to trial Office 365, then you may ask "How do I keep control of my documents?"
Documents that you create belong fully to you.
You can choose to store them online using Microsoft OneDrive, or locally on your PC or Mac.
If you cancel your subscription or if it expires, you can still access and download all your files by signing in to OneDrive directly using the Microsoft account you used to set up Office 365. If your files exceed the free 15 GB of storage, then you will want to purchase more OneDrive space, or simply save your files elsewhere.