Once an edition's paperback or hardcover is built, Preview next to its download opens its pages as the printed book opens: page 1 on its own on the right, then each left-hand page beside the right-hand page it faces. Turn with the arrows, the arrow keys or a click on either page, drag the slider, or type a page number. One page shows a page at a time, for a small screen.
Trim and margins draws what printing does to each page:
- Trim: the blue line, where the page is cut.
- Where the cut may land: printing and trimming can move the cut up to 1/8 inch (3.2 mm), so nothing that matters should sit in the hatched band inside the trim.
- Gutter: the inside margin, at the binding. KDP asks for more of it the thicker the book: 0.375 inch up to 150 pages, 0.5 inch up to 300, 0.625 inch up to 500, 0.75 inch up to 700 and 0.875 inch above that.
- KDP's margins: the dashed line, at least 0.25 inch from the trim at the top, the bottom and the outside, and the gutter at the inside. Text, page numbers and pictures go inside it.
Where the build's check found ink outside KDP's margins, the page is outlined in red and listed above the pages: KDP won't take the file until what's there moves inside the dashed line.
The pages show on the paper you chose, cream or white, with the binding's shadow at the fold. Actual size shows them as large as the printed book, once you measure the screen against a bank card; the cover editor's 3D proof uses the same measure. Zoom in to look at the type, and drag to move around the pages.
It's the same PDF you'll upload, so it shows what prints. KDP's own previewer checks the file again when you upload it, and a printed proof copy shows the paper and binding in your hands.