hexo-theme-doc is described as 'documentation theme for Hexo, the fast and powerful blog framework powered by Node.js. It differs from other Hexo themes by allowing you to present documentation—especially REST API documentation'. There are more than 25 alternatives to hexo-theme-doc for a variety of platforms, including Self-Hosted solutions, Linux, Mac, Windows and Online / Web-based. The best alternative is GitBook, which is free. Other great apps like hexo-theme-doc are MkDocs (Free, Open Source), Daux.io (Free, Open Source), Docsify.js (Free, Open Source) and Archivy (Free, Open Source).
Daux.io is a documentation generator that uses a simple folder structure and Markdown files to create custom documentation on the fly. It helps you create great looking documentation in a developer friendly way.
docsify generates your documentation website on the fly. Unlike GitBook, it does not generate static html files. Instead, it smartly loads and parses your Markdown files and displays them as website. All you need to do is create an index.
A documentation generator that builds HTML output based on Markdown files. Supports Markdown specs and offers a wide set of custom components using Markdown-like syntax. Builds Reference Source documentation for .NET projects (more added soon).