> Sorry, but the Wiki content is not really a documentation set.

Besides

> that, we still need PDFs and HTMLs, i.e. LangRef, ApiGuide, etc. And
> they're likely to be bound to FB versions. How do you suggest to

create

> them from the Wiki contents which is supposed to have a mixture of
> various information inside the every topic?
>

That's simple. A good engine (like wikka for instance -- I use it for
years) is extensible in at least two aspects: "actions" and
"formatters". Actions are little scripts embedded in the markup, sorta
like {{image url="some-image"}} to show an image, or {{files}} to show
file attachments, while formatters are scripts that embed markup, and
transform it somehow, sorta like %%(very-special-text)this text will
be displayed differently, saved to a database or whatever%%.

So it's just a matter of inventing your own "actions" and "formatters"
to augment semantics of various paragraphs. It's like phpDocumentor
tags, if you like.