I like to use Markdown for authoring (it's a lot simpler than LaTeX!), but use Pandoc to convert to PDF (which uses a LaTeX template).
If needed, you can also sprinkle the Markdown with LaTeX, such as to enforce page breaks at specific points.
On the other hand, if you already know the gist of Markdown, then you could pick up reStructuredText or AsciiDoc in less than an hour. They're more feature-rich than markdown, without adding too much squeeze for the juice.