The Making of Day of the Daleks - Special Edition is a documentary included on the DVD release of Day of the Daleks. It covers the restoration and upgrade of the BBC Library copy of the story. It goes into great detail on how and why they made the Re-edit.
For the purposes of this list, a "DVD documentary" is one made especially for the Classic Series DVD range. For this reason, things like studio recordings, film trims/inserts and other documentaries featured on DVD releases are not included below.