Layout and Imposition
 

   
 

Page 1, Page 2, Page 3, Page 4 ... that's the order in which we read a book or booklet. But is that the way we print them? Not always.

Sometimes pages must be printed out of order. On this and subsequent pages take a look at some simple examples that demonstrate imposition or printer spreads -- the process of printing multiple pages on a piece of paper in such a way that when folded (and perhaps cut) they end up in proper 1, 2, 3, 4 order for readers.

See the first illustration of a simple 4 page booklet printed above. Add 4 more pages to that booklet and your page numbering changes as shown in the second illustration.

Software designed specifically for creating books and booklets often handles the page layout and printing automatically. However if you are using a graphics or page layout program that doesn't, see the third illustration for how you would layout a side-folding greeting card printed on 1 side of a letter-size paper.

Commercial printers often use large sheets of paper that they fold, cut, and trim to the finished size. One of many possible ways of printing multiple pages is shown in this illustration..

This example is a 16-page "sheetwise imposition" signature. One large sheet is printed with 8 pages on each side. The solid lines are for cutting. The dashed lines are where the paper is folded. Once cut and folded the pages form a 16 page booklet or signature. Several such signatures may be assembled into the final book or other publication.
 
Plan for colour and graphics with imposition knowledge
Knowing how commercial printers position your pages for printing can be an important planning factor when it comes to adding colour and spreading graphics across a 2-page spread.  As with any job, consult your printer early in the planning process to insure good results and to make sure that your job doesn't involve processes that your printer cannot handle.

Reduce the cost of four-color process printing
If planning a publication that mixes black and white with some four-color process illustrations -- plan all colour so that it falls on one side of a press sheet or all within a single signature when the job consists of multiple signatures.

Insure smooth page-to-page transition of photos and graphics
If the pages of your booklet are not exactly aligned, an image or graphic that is finishes exactly on the booklet fold line may unintentionally cross and will be partially visible on another page in the final assembled document. Wherever possible, design your graphics so to reduce any problems across the fold.

Make a Mockup
Even before you start designing the pages, cut up and assemble a tiny mockup of your book, newsletter, or booklet and number the pages so that you can see both the printing order and the reading order of your pages. This can be invaluable when planning use of colour and placement of graphics.

Print Thumbnail Pages
Whether printing from your desktop or using a commercial printer, create thumbnails of your publication. In fact, your printer may require a folded dummy or a signature sheet showing positioning of pages.

Check the Chart
These diagrams shows printer spreads and number sequences for 8 and 16 page booklets. TIP: The two page numbers that are imposed side-by-side always add up to 1 more than the total number of pages in the booklet. For example, in an 8-page booklet all pairs of pages add up to 9 [8+1,6+3].
  

 8 page booklet; two sheets of paper

Front of Sheet   Back of Sheet
8 1   2 7
Page 2 is directly behind Page 1.
6 3   4 5
Page 4-5 is your centre spread.

 

 16 page booklet; four sheets of paper

Front of Sheet   Back of Sheet
16 1   2 15
14 3 4 13
12 5 6 11
10 7 8 9
Page 8-9 is your centre spread.
 
Creep
In a saddle stitched booklet the bulk of the paper causes the inner pages to extend further out than the outer pages when folded. When trimmed the inner pages are narrower than the outer pages.

The illustration opposite shows an exaggerated view of how the inner pages of a saddle stitched booklet "creep" out and extend beyond the edge of the outer pages when folded.

Creep varies depending on the thickness of the paper and the number of pages.  If there is no creep allowance, when pages are trimmed on the guillotine the pages towards the centre of the book become narrower, and there is the possibility that text or images may be cut off.
If creep is noticeable, the images and text can be repositioned towards the fold of the booklet pages, so that they have the same outer margins.  Some page layout software can automatically calculate and adjust layouts for creep.