A printed book is read as a spread: two facing pages, a left and a right, with the gutter down the middle. It is how margins are set, how chapter openers are placed, and how a reader actually meets your words. Most editors never show you that view until the file is done.
Two-Page Spread puts it in front of you while you write. Toggle Spread in the typography popover and the single-page editor becomes an open book: verso on the left, recto on the right, reflowing live with every keystroke. There is no compile step and no separate preview. The spread you draft into is the spread you export.
Folios and running heads, placed for you
Page numbers sit on the outer corners. Running heads alternate the way they do in a real book: the book title on the left page, the chapter title on the right. New chapters open on the recto automatically. You are not formatting any of this by hand; the page does what a typesetter would do, as you type.
Flip, don't scroll
The on-screen flip arrows and the status-bar navigator move between spreads with a short slide, so reading ahead feels like turning pages rather than scrolling a document. Your cursor stays where you left it, and a small pill reminds you where it is when you have flipped away. Press Escape to jump straight back to it.
Built on the real engine
The spread is not a formatting layer bolted onto the editor. It uses the same pagination engine, trim sizes, margins, and typographic rules as your PDF export, so what you see is what prints. Long manuscripts open quickly and stay responsive as you type, and snapshots work in spread mode just as they do anywhere else.