Check your margins before you print
Print needs room the screen never shows: a margin for the bindery, a safe area inside it for anything that must not meet the guillotine. Drop a PDF here and its pages render in this tab — pdfjs, the same engine the site's library reader uses — with dashed guides drawn over them at your margins. What fits and what doesn't stops being a guess. Rendered on this machine; the file never uploads.
The two lines
Trim margin (red dashes)
The no-art zone at the page's edge. Text outside it may be shaved in trimming; full-bleed art should CROSS it deliberately, not accidentally.
Safe area (gold dashes)
Inside the margin: folios, captions, anything that must survive. The studio's chat books work to 15 mm outside, 5 mm inside it — the defaults.
The binding edge is special
Bound books lose extra room to the gutter — the fold eats margin the outside edges don't. Check your worst spread, not your favourite page.
The tool renders and draws; it does not judge. Automatic content-detection on arbitrary PDFs means guessing at text bounds — and a guess about margins is worse than eyes on the page. Flip through, look at the guides, and the page tells you. When the margins hold, take the file for crop marks; when they don't, back to the layout tool.
Questions people actually ask
Does my PDF get uploaded anywhere?
No. Rendering happens in this tab with the same engine the library reader uses, and the file stays in your browser's memory throughout.
What margin should I use?
For bound books: 15–20 mm, plus extra on the binding edge. Zines tolerate 12; classical typography likes 25. The presets cover the common cases and the box takes any figure.
Can it fix margins that are too small?
No — margins are made in the layout, not in the PDF. This shows you the problem early, where fixing it is a paragraph of work rather than a reprint.
Why does page one look different from my PDF viewer?
You're seeing it at fit-to-width without smoothing shortcuts — close enough to judge margins. The millimetre readout under the controls is the page's true size; the guides are drawn against that truth.
The studio sets chat books at 15 mm and shows you the proof.
See a proof — freeThis is one of the tools — or see everything we’ve written.