Asciidoctor supports several output formats: https://asciidoctor.org/docs/user-manual/#selecting-an-output-format
An output format of PDF is possible but requires the asciidoctor-pdf gem: https://rubygems.org/gems/asciidoctor-pdf
Please add asciidoctor-pdf as an optional runtime dependency.
This gem does not have a proper release yet and it depends on a lot of unmaintained code (all of prawn), some of which is also unpackaged. In any case I would like to wait until there is a official release, and at that time we can also assess the state of the dependencies.
Asciidoctor PDF now appears to have proper releases. The latest version now is 1.5.3.