What the file contains
Every page of the book in reading order, on a page whose MediaBox is trim plus bleed and whose TrimBox is the trim, which is the file most printers ask for. Uploads go in at print resolution with the layout you set in the page editor; drawings are rendered at print size without the thumbnail and pencil layers; empty pages go in blank. Cover pages go in when Include cover pages is on, the default for saddle stitch, and a missing inside cover goes in as a white page so page 1 stays a right-hand page. Perfect-bound printers usually want the interior on its own and the wraparound cover from the cover calculator as a separate file. On a left-hand page the TrimBox sits one outer bleed in from the left, so printer specs with no bleed on the spine side come out right. An optional CMYK simulation pulls colours into the press gamut and tags the file for a SWOP press; the pages themselves stay RGB, and with it on every page is re-encoded as a high-quality JPEG. Spreads put two pages on one sheet with outer bleed only, first page alone on the right. Booklet mode lays pages out on double-wide sheets in saddle-stitch order (page 8 next to page 1, and so on) at trim size, for printing double-sided at home, folding and stapling. A booklet always includes its covers, with any padding blanks before the back covers. Each sheet is two trims wide (13.25 x 10.25 in for a US comic), so print it on tabloid or A3, or fit to page on Letter or A4. The assembly happens in your browser from signed links to your private files. Run the result through the PDF preflight before ordering.