If you're not sure whether Jekyll and this theme will support your requirements, this list provides a semi-comprehensive overview of available features.
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Before you get into exploring Jekyll as a potential platform for help content, you may be wondering if it supports some basic features. The following table shows what is supported in Jekyll and this theme.

Features Supported Notes
Content re-use Yes Supports re-use through Liquid. You can re-use variables, snippets of code, entire pages, and more. In DITA speak, this includes conref and keyref.
Markdown Yes You can author content using Markdown syntax. This is a wiki-like syntax for HTML that you can probably pick up in 10 minutes. Where Markdown falls short, you can use HTML. Where HTML falls short, you use Liquid, which is a scripting that allows you to incorporate more advanced logic.
Responsive design Yes Uses Bootstrap framework.
Translation Yes I haven't done a translation project yet (just a pilot test). Here's the basic approach: Export the pages and send them to a translation agency. Then create a new project for that language and insert the translated pages. Everything will be translated.
PDF Yes You can generate PDFs from your Jekyll site. This theme uses Prince XML (costs $495) to do the PDF conversion task. You basically set up a page that uses Liquid logic to get all the pages you want, and then you use PrinceXML (not part of Jekyll) to convert that page into a PDF.
Collaboration Yes You collaborate with Jekyll projects the same way that developers collaborate with software projects. (You don't need a CMS.) Because you're working with text file formats, you can use any version control software (Git, Mercurial, Perforce, Bitbucket, etc.) as a CMS for your files.
Scalability Yes Your site can scale to any size. It's up to you to determine how you will design the information architecture for your thousands of pages. You can choose what you display at first, second, third, fourth, and more levels, etc. Note that when your project has thousands of pages, the build time will be longer (maybe 1 minute per thousand pages?). It really depends on how many for loops you have iterating through the pages.
Lightweight architecture Yes You don't need a LAMP stack (Linux, Apache, MySQL, PHP) architecture to get your site running. All of the building is done on your own machine, and you then push the static HTML files onto a server.
Multichannel output Yes This term can mean a number of things, but let's say you have 10 different sites you want to generate from the same source. Maybe you have 7 different versions of your product, and 3 different locations. You can assemble your Jekyll site with various configurations, variants, and more. Jekyll actually does all of this quite well. Just specify a different config file for each unique build.
Skinnability Yes You can skin your Jekyll site to look identical to pretty much any other site online. If you have a UX team, they can really skin and design the site using all the tools familiar to the modern designer -- JavaScript, HTML5, CSS, jQuery, and more. Jekyll is built on the modern web development stack rather than the XML stack (XSLT, XPath, XQuery).
Support Yes The community for your Jekyll site isn't so much other tech writers (as is the case with DITA) but rather the wider web development community. Jekyll Talk is a great resource. So is Stack Overflow.
Blogging features No This theme just uses pages, not posts. I may integrate in post features in the future, but the theme really wasn't designed with posts in mind. If you want a post version of the site, you can clone my blog theme, which is highly similar in that it's based on Bootstrap, but it uses posts to drive most of the features. I wanted to keep the project files simple.
CMS interface No Unlike with WordPress, you don't log into an interface and navigate to your files. You work with text files and preview the site dynamically in your browser. Don't worry -- this is part of the simplicy that makes Jekyll awesome. I recommend using WebStorm as your text editor.
WYSIWYG interface No, but ... As noted in the previous point, I use WebStorm to author content, because I like working in text file formats. But you can use any Markdown editor you want (e.g., Lightpaper for Mac, Marked) to author your content.
Versioning Yes, but... Jekyll doesn't version your files. You upload your files to a version control system such as Git. Your files are versioned there.
PC platform Yes, but ... Jekyll isn't officially supported on Windows, and since I'm on a Mac, I haven't tried using Jekyll on Windows. See this page in Jekyllrb help for details about installing and running Jekyll on a Windows machine. A couple of Windows users who have contacted me have been unsuccessful in installing Jekyll on Windows, so beware. In the configuration files, use rouge instead of pygments (which is Python-based) to avoid conflicts.
jQuery plugins Yes You can use any jQuery plugins you and other JavaScript, CMS, or templating tools. However, note that if you use Ruby plugins, you can't directly host the source files on Github Pages because Github Pages doesn't allow Ruby plugins. Instead, you can just push your output to any web server. If you're not planning to use Github Pages, there are no restrictions on any plugins of any sort. Jekyll makes it super easy to integrate every kind of plugin imaginable. This theme doesn't actually use any plugins, so you can publish on Github if you want.
Bootstrap integration Yes This theme is built on Bootstrap. If you don't know what Bootstrap is, basically this means there are hundreds of pre-built components, styles, and other elements that you can simply drop into your site. For example, the responsive quality of the site comes about from the Bootstrap code base.
Fast-loading pages Yes This is one of the Jekyll's strengths. Because the files are static, they loading extremely fast, approximately 0.5 seconds per page. You can't beat this for performance. (A typically database-driven site like WordPress averages about 2.5 + seconds loading time per page.) Because the pages are all static, it means they are also extremely secure. You won't get hacked like you might with a WordPress site.
Relative links Yes This theme is built entirely with relative links, which means you can easily move the files from one folder to the next and it will still display. You don't need to view the site on a web server either -- you can view it locally just clicking the files. This relative link structure facilitates scenarios where you need to archive versions of content or move the files from one directory (a test directory) to another (such as a production directory).
Themes Yes You can have different themes for different outputs. If you know CSS, theming both the web and print outputs is pretty easy.
Open source Yes This theme is entirely open source. Every piece of code is open, viewable, and editable. Note that this openness comes at a price — it's easy to make changes that break the theme or otherwise cause errors.