FAST-Help

Fast-Help is a Windows Help File Generator that produces online and offline documentation. Compile to any of the following formats, all from a single source editor.

That means you type once and compile to whatever format you need.
Format:
-HtmlHelp (.CHM)
-WinHelp (.HLP)
-Website Help
-Printable Manuals
-MS Word Manuals
-PDF
-Windows Mobile Help
-wxWidgets Help