Quill
a what-you-see-is-what-you-need editor with clean display of your content and subtle presentation of semantic markup. It also has live preview and navigation support, though those are supportive; the real point is that it's an editor.

Parchment
a simple but powerful rendering back-end which takes these documents and outputs them as PDF files. Different document types have different rendering engines (ie, stylesheets) customized for the purpose.