Imposition is the arrangement of pages on a printed sheet which when folded in the correct sequence form a section of a book.

The number of pages in a section or signature as it is also known is determined by the size of the sheet to be printed on and the trim size of the book. These sections are either 32pp, 16pp or 8pp. It is important to understand the basics of imposition since it can have an important bearing on the design of a book, particularly where bleeds are concerned.

When planning for bleeds and deciding on the margins of a book layout, you must consider the direction in which the sheet will travel through a printing machine as allowances need to be made for the areas which do not print known as the 'grips'. These areas of the sheet are held by the printing machine as it travels through it and subsequently are not able to be printed. What you need to avoid is areas that bleed or are too close to the trim of the book, falling into the 'grips', or you will need to buy oversized or non-standard size paper to accommodate the design thereby increasing costs.

As a rule of thumb our presses require 13mm of white paper on both the leading and trailing edges in which no image should appear (this includes our standard 3mm trim). The important margins to consider are the