Admin · Courses
Where: Courses → Unit library → open the unit → open the document
What happens next While you work on the draft, students keep seeing the published version. Nothing changes for them until you publish. Publishing creates a new version, and every course using this unit picks it up. The older version stays in the history.
Why there is no "unpublish" Students may already be using the published version, so it can't be switched back to a draft. If you need students to stop seeing it, retire it instead (see "Retire learning material students should no longer see").
If something looks wrong If your changes don't show for students, check you published the draft, not just saved it. If the page says "A newer draft is in progress", carry on editing that draft rather than starting another.