Indicating Changed Text in Help Files
http://www.hyperwrite.com/Articles/showarticle.aspx?id=30

Self, Tony
HyperWrite
2004

Abstract:

There are still many circumstances when drawing a user's attention to changed text is important. How do we do that with Help systems? By borrowing techniques from paper manuals, we don't have to reinvent the wheel. So here's a good approach that will work for Microsoft Word-based HATs.