A saddle-stitched booklet is made of sheets folded in half, nested inside each other and stapled through the fold. Because the sheets nest, the pages that print side by side are not in reading order. This arrangement is called printer spreads.
The rule: pairs that add up to "pages + 1"
For a booklet of N pages, every pair of pages printed side by side adds up to N + 1. In a 12-page booklet, page 12 sits next to page 1, page 2 next to 11, page 10 next to 3, and so on.
8-page booklet (2 sheets)
| Sheet | Front (left | right) | Back (left | right) |
|---|---|---|
| 1 (outer) | 8 | 1 | 2 | 7 |
| 2 (inner) | 6 | 3 | 4 | 5 |
12-page booklet (3 sheets)
| Sheet | Front | Back |
|---|---|---|
| 1 | 12 | 1 | 2 | 11 |
| 2 | 10 | 3 | 4 | 9 |
| 3 | 8 | 5 | 6 | 7 |
Each sheet carries 4 pages, so the page count must be a multiple of 4.
When the page count isn't a multiple of 4
Add blank pages to reach the next multiple of 4. Put them before the back cover, not after it, so the back cover stays on the outside of the booklet. A 10-page file becomes 12 pages with two blanks as pages 10 and 11.
Creep: why inner pages need to move
In a thick booklet the inner sheets stick out further at the open edge than the outer ones (the paper thickness pushes them outward). After trimming, the inner pages lose more of their outer margin. Creep compensation shifts the inner pages slightly toward the spine to balance this. Thin booklets of 8–16 pages rarely need it; for 40+ pages or heavy paper, try 0.5–1 mm total.
Sheet size and scaling
Two A4 pages exactly fill an A3 sheet (420 × 297 mm), which leaves no room for margins, gripper or crop marks. Either print on SRA3 (full size with room for marks) or scale the pages down slightly (around 93% on A3 with crop marks). Remember the finished booklet is then a little smaller than A4.
Do it in seconds with ImpoGrid
Choose Booklet, open the PDF, and ImpoGrid builds every sheet's front and back in the right order, adds blanks before the back cover, applies creep, and adds crop and fold marks. Step through every plate before you download.
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