A Signature is a configuration printers use to layout booklet/book pages on a press sheet so that after folding they are in the correct order. For saddle-stitched books and booklets, a signature cannot be less than 4 pages. Depending on the finished size of the publication, signatures may be as large as 32 pages.
The following is an imposition layout for a 16-page signature. You’ll note the pages look out of order and half the pages are upside down…exactly as they need to be for folding and ending up in the right order.
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Simplified Examples
If an order calls for a 16-page self-cover 8.5” x 11” saddle-stitched booklet, the graphic shows exactly how the pages would be imposed on a 24” x 36” or larger press sheet. Once printed, the sheet would be folded to 18” x 24”, then right angle folded to 18” x 12” and right angle folded again to 9” x 12.” The booklet is now ready for saddle stitching and trimming on three sides down to its 8.5” x 11” finished size.
If the specifications for a saddle-stitched booklet called for 32 pages rather than 16, it would require two 16-page signatures. Rather than either signature laid out like the above graphic, one signature would contain page numbers 1 through 8 and 25 through 32. The second signature would contain pages 9 through 24. This second signature would nest inside the first signature creating 32 pages.
Economy of Signatures
It is always best to check with your printer about print economies when starting a new project. For example, if your booklet will be 44 pages self-cover, 8.5” X 11”, you will have 2 sets of plates (16-page signatures) for the first 32 pages, another set of plates for the next 8 pages, and yet another set of plates for the last 4 pages taking the count to 44 pages.
Depending on the number of booklets you will order, your total cost for a 44-page may be more than if you ordered a 48-page (3 16-page signatures). Extra plates and folder set-ups may very well cost more than the paper cost of the extra 4 pages for printing 48 pages.
Terms Relevant to Booklet and Book Production
A leaf is a sheet of paper bound into a book. A leaf always contains two pages. A page is one side of a leaf whether printed or not.
Imposition is the electronic placement of pages in their proper position on a press sheet. This applies to laying out the pagination for a booklet or book so that when the press sheet is folded the pages are in the correct order and with adequate trim.
Self-cover booklet indicates there is to be no additional cover. All pages of the booklet will be printed on the same stock. Example: 32 pages self-cover. In this case, the printer will receive one file containing 32 individual pages.
Booklet plus cover indicates there is to be a cover, usually of a heavier weight, in addition to the pages. Example: 32 pages plus cover. The cover is always assumed to be 4 pages. In this case, the printer will receive two files – one containing 32 individual pages and another file containing the 4 cover pages.
Press Sheets are the sheets of paper, or other substrates, that a project is printed on. In the case of digital printing, the press sheet may be 14” x 20”. Larger commercial printers usually have 40” presses that accommodate 28” x 40” sheets. Between and around the pages imposed on the sheet there are usually trim areas known as gutters. These gutters allow for trimming during the bindery/finishing process.
In addition to live matter, press sheets contain registration marks and printer color bars for scanning to maintain consistent color. There must always be allowance on the lead edge for gripping the sheet to guide it through the press.
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