·A single color page printed in color by a four-color printing machine is generally a paper promotional material made to expand its influence.·There are two folds, three folds, four folds, five folds, six folds, etc. In special circumstances, manual folds can also be added to the process that cannot be folded by the machine.·The total number of pages is not much, so when binding is inconvenient, it can be made into folds; in order to improve the design beautification effect or facilitate content classification, small folds can also be made, such as the 16K three-fold; in order to meet environmental protection requirements, many simple instructions are now adopted in the form of folds without riding and binding