What is imposition in printing?

A press does not print one business card at a time. It prints a large sheet carrying as many copies as will fit, and that sheet is then cut down. How efficiently the copies nest is one of the biggest levers on the unit price of a printed job, and it is entirely invisible to the customer.

The arithmetic is unforgiving in a useful way. If a design allows twenty-one copies per sheet rather than twenty, a ten-thousand-piece run needs roughly twenty-four fewer sheets — plus the ink, the press time and the waste that goes with them. Conversely, a finished size chosen for aesthetic reasons that happens to leave a wide unusable strip on every sheet is quietly paid for on every unit.

This is why it is worth asking, before the design is finalised, whether a few millimetres either way on the finished size would improve the layout. On a short run it makes little difference. On a long one it can be the difference between two quotes.

For multi-page work imposition also handles sequence. Pages are not laid out in reading order but in the order that produces correct pagination once the sheet is folded and trimmed — which is why a page count that is a multiple of four is cheaper than one that is not.