Present mode
Turn any document into a fullscreen slideshow with one click – choose the option to “Present” from the document menu in the top right. The document content will scale to fit the screen and the document title becomes it’s own slide.

Find "Present" in the document and command menu
How it works
When presenting the document is split into slides based on headings and dividers (---). All the usual shortcuts from other presentation tools work too:
Space: Next slideArrow right: Next slideArrow left: Previous slidePage Down: Next slidePage Up: Previous slideHome: Go to firstEnd: Got to lastf: Enter fullscreenEscape: Leave fullscreen