What are some alternatives?
Dr.Explain - Dr.Explain software is a help file authoring tool.
Airim - Show personalised FAQs before live chat
HelpNDoc - What is HelpNDoc ? Easy to use yet powerful help authoring environment which can generate various documentation formats from a single source.
Doc-O-Matic - Doc-O-Matic is a software source code documentation and Help authoring tool.
MadCap Flare - Documentation for Any Audience, Language or Format
Adobe RoboHelp - Adobe RoboHelp empowers organizations to deliver engaging help and policy content across mobile devices, formats, and platforms.