Folding depends on the binding process and the sheet size. Ordinary folding machine can do a fold to four folds page, hand folding is not limited. Less than 100 grams of paper can be used for four-fold sheets, 100 grams or more should not exceed three-fold sheets. More than 200 grams of paper can be folded manually after the die-cutting machine to achieve folding. A book may adopt different folding methods in different factories. Therefore, it is best to make sure that the page numbering of a folded handprint is determined by the professional of the printing factory. The corners are arranged at the hinges of the sheet and are called heads. For a book, the same specification leaflet must be used uniformly, that is, the days of the folded pages are all at one end of the fold line and the feet are at the burrs. Can also be arranged on foot. When the plate outputting film is determined, the double-P output of the adjacent page of the folded sheet and the printed sheet is determined to be better (the nails are in the middle of the 2P), which can improve the ergonomics and precision of the imposition, and reduce the patchwork seam. If the double P is ordered by the pages of the book, it will increase the work of the piece because the page numbering of the folded pages (imposed) is not the same as the original page order.