How do I upload a new version of a file in Resources?
If a file is linked and active elsewhere in your course site - such as in a Lessons module or an image in a quiz - deleting it from Resources and uploading a new file in its place will break the link. By uploading a new version, your existing links remain intact.
Click Actions, then Upload New Version.

To upload a new version of a file, to the right of the file to replace, from the Actions drop-down menu, select Upload New Version.
This displays the Upload New Version page.