What Are Folding Signatures

It is helpful to have insight into how commercial printers use "signatures" when they lay out large press sheets for booklets and books. Customers and designers have no responsibility for the creation of signatures (layouts) that will be used in the printing process. The printer's powerful prepress software takes care of it. With today's technology, almost all commercial printers want files submitted as single pages with bleeds set, and their sophisticated imposition programs take it from there.

Flat Pile Combination Folding Machine

Gantry Pallet Combination Folding Machine

Round Pile Combination Folding Machine

Here, we discuss signatures used by commercial printers for two types of bound publications:

Booklets:

The term "booklet" refers to saddle-stitched booklets. This includes any publication stapled on the spine such as magazines, programs, brochures, catalogs, newsletters, etc. 

If all of the pages of a booklet are on the same paper it is referred to as a self-cover booklet. 

If the booklet has a cover printed on a different stock, usually heavier, it is referred to as a booklet plus cover. Examples: 16-page self-cover vs. 16-page plus cover.

Books:

The term "book" refers to two types of books. 

A) Perfect-bound books, commonly called paperback, have a flat spine with a heavier cover wrapped around text pages which are glued to the cover at the spine. Personal and business self-help books, novels, and reference books are examples. 

B) Casebound books (often called hardcover books) have a hard paper board cover wrapped in paper and sometimes cloth. The pages are frequently sewn and sometimes glued at the spine. These are easily found on bookstore shelves and libraries.

CP Round Pile Buckle Folding Machine

CP Flat Pile Buckle Folding Machine

CP Gantry Pallet Buckle Folding Machine

What Is a Printer's Signature?

A Printer's Signature is a configuration printers use to lay out booklets and book pages on a press sheet so that after precision folding they are in the correct order. Depending on the finished size, signatures are typically 4, 8, 16, and 32 pages per press sheet.

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.

16-page signature

Simplified Examples

Saddle-Stitched Booklets

If an order calls for a 16-page self-cover 8.5"×11" saddle-stitched booklet, the graphic shows exactly how the pages would be imposed on a 24"×36" or larger press sheet. Once printed, the sheet would be folded to 18"×24", then the right angle folded to 18"×12", and the right angle folded again to 9"×12".  The booklet is now ready for saddle-stitching (stapling) and trimming on three sides down to its 8.5"×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.

Independent Folding Knife

Signature configuration

Perfect Bound and Case Bound Books

Signatures for these types of books are similar to those used for booklets. The major difference is that instead of nesting each subsequent signature inside the previous, these signatures stack on top of each other. The first signature would contain pages 1-16, the second would contain 17-32, etc.

Economy of Signatures

It is always best to check with your printer about print economies when starting a new project. For example, if your saddle-stitched booklet will be 44 pages self-cover, 8.5"× 11", you will have 2 sets of plates (2 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.

44-page signature

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"×20". Larger commercial printers usually have 40" presses that accommodate 28"×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.

Print Markings