Paper size refers to the size range of the paper that the folding machine can support, generally including a maximum size and a minimum size, which are generally expressed by paper specifications. If the paper is larger or smaller than this size range, the product cannot be folded and collated.

Folios are usually divided into three types according to their size: large folios, medium folios and small folios. For 787×1092 paper, a large format is more than 12 karats, a medium format is 16 to 36 karats, and a small format is below 40 karats. However, text-based books are generally medium format.

Except for 6-karat, 12-karat, 20-karat, 24-karat, and 40-karat format, the format is rectangular with different proportions, which are suitable for various books of different nature and purpose.