APIDOC
APIDOC is a tool for writing API documentation. It was originally created to document the JavaScript engine, but is meant to be generic enough to document other APIs.
The source for APIDOC is checked into the Mozilla source repository in the directory mozilla/webtools/apidoc
The APIDOC documentation (created with APIDOC) is available as:
New Voice Media has created an XSL transform to turn APIDOC source into PDF. Check it out. The APIDOC documentation, translated to PDF, can be had here [PDF].
Please send comments, suggestions, or patches to the author.