Thanks for your responses folks, some good points raised there.
I'm aiming to write it for a generic 3D modeling program not just based on Truespace. I'm going more for what to do with the tools rather than repeating information that may be found in your software's help files.
Regarding format I'm currently writing it in HTML. I want to make it easy to cross reference, navigate and link between sections. Can I do that in Adobe Acrobat PDF format? If so can I convert HTM to that format?
Thanks