Indeed, O'Reilly now uses Asciidoctor as the basis of their Atlas authoring system. They go directly from AsciiDoc text, by way of Asciidoctor, to HTML, and from there to PDF, epub, and other digital formats. When I write my books for O'Reilly, I can use their system to generate for myself a PDF of the manuscript at any time. When the book is finished, it is this very same PDF that is sent to the publisher for just-in-time dead-tree publication. When a customer buys a paper copy of my books at Amazon, what that customer sees on the page is exactly what I saw in the PDF I generated straight from AsciiDoc text.
See also my post here:
http://discuss.asciidoctor.org/O-Reilly-Atlas-tp872p4640.html