The DevExpress ASP.NET Rich Text Editor (ASPxRichEdit) provides the Simple View mode to display documents ignoring the page's layout. In this mode, the control adjusts the document so that it occupies the entire control's content area.
You can enable the Simple View mode in the following ways:
Click the Simple View Ribbon's command
Execute the changeViewType client command
Set the ViewType server-side property to Simple
This demo illustrates how the document's layout is adapted to the control's width when the Rich Edit is in the Simple View mode. Drag the vertical slider to change the ASPxRichEdit's width and see how the document fits the control.