There are many cloud services where you can backup your files for free. Like Dropbox, Googledrive, Onedrive, Box etc.
Dropbox is my favourite because its reliable, easy to use and a breeze to setup.
When you install, the app is in your file system, meaning you can easily move files from your ipad or desktop to cloud and vice versa by dragging and dropping in your Dropbox folder.
Its free unless you're storing TB's of data.