Next up in the Fade series is fading an underlay. All sorts of underlays can be faded -- DWF, DGN, PDF, and images. You can fade whatever underlay types your version supports (DWF in LT 2007, DWF and DGN in LT 2008, etc.).
In AutoCAD LT 2010, you can set fading with the Adjust command on the Reference Panel of the Insert tab. In other releases, you can use the ###ADJUST commands (like DWFADJUST) or the Properties palette.
Valid values for fading underlays are from 0 to 100.
(Note: Fading is not the same thing as transparency. A faded underlay will still obscure objects behind it.)