Save versions of a document or workbook

Tasklist allows you to save a version of a document or workbook.  You can do this from the backstage view, by pressing Save to Tasklist:

This gives you two options:

Save as a new version saves the document as a new version of the same document.  You might use this to save successive drafts of a document you are working on.

Save as new version of another document allows you to select the document to use as the original for this new version.  This is useful if you send a document to someone, who sends it back to you with edits.  You might want to save the document you receive as a new version of your original document.