In one example in accordance with the present disclosure, a printing system is described. The printing system includes multiple print engines to form printed marks on a substrate. Each print engine prints non-sequential pages of a print job. A sensor of the printing system detects, for each page, a trailing edge gap size and a leading edge gap size. A controller of the printing system, based on a difference between trailing edge gap sizes and leading edge gap sizes for a set of pages of a print job, adjusts a printing operation to equalize subsequent trailing edge gap sizes and leading edge gap sizes.