When it comes to creating technical content, you have three categories of applications to choose from:
Adobe FrameMaker fits into the middle category of long doc applications. It has the word processing you'd expect from something from MS Word, but has consistent and very customizable numbering, referencing, and book functionality.
FrameMaker can also do the job of many other specialized editors. FrameMaker is a structured editor, capable of working with XML models like DITA, S1000D, and various MIL-SPEC standards. FrameMaker easily handles custom XML and SGML content models as well.
FrameMaker also publishes high-quality PDF, HTML5, and mobile applications for iOS and Android devices.
Here's a quick run-through of these concepts in FrameMaker