The user guide of visitors is located until now on contaowiki.org/Visitors, in German and in English.
Contao manages the Docs on GitHub using Markdown files and export them to HTML and PDF.
I've also tried now.

Here you can look at the experiment: http://docs.contao.ninja/en/visitors.html

Benefits are:
  • In GitHub you can submit corrections and new translations
  • There is an export to PDF, an export is possible in eBook format. (theoretically)
  • A search is possible directly in the manual (HTML / PDF)
  • Fonts can be switched bigger / smaller

In the Wiki I would then continue the manual in a short form with a link to my page.

What do you say?