The space between the editor and the text is created by the Spacer control
<?xml version="1.0" encoding="utf-8"?>
<mx:Application xmlns:mx="http://www.adobe.com/2006/mxml">
<mx:RichTextEditor id="myEditor" title="My Rich Text Editor">
<mx:htmlText>
this is a test
</mx:htmlText>
</mx:RichTextEditor>
<mx:Spacer height="50"/>
<mx:Text text="{myEditor.htmlText}" width="{myEditor.width}"/>
</mx:Application>