Turns out the guide is no longer relevant, and instead people should reference the resources at Digital Publishing Solution Help. We just forgot to update that link, oops! It'll be refreshed around midnight tonight to point to the correct new location.
He, he – you are right about the HTML Help. But, this is why I saw the broken link: I wanted to load the PDF to my iPad in order to read it on my flight back tonight. So I'm at the gate now still enough time to load it to the iPad