Booklet ImposerGutter vs Creep
Two different problems
Gutter and creep are not nicknames for the same margin. Gutter is space you add next to the staple so type and images do not sit in the bind. Creep (shingling) is a shift that grows with nested sheets: the outer sheet wraps a thicker pile, so its content would sit closer to the trim if you did nothing.
| Gutter | Creep | |
|---|---|---|
| Purpose | Keep content out of the stitch | Keep outer and inner trim margins even |
| This tool | Millimeters per spine side | Total creep toward the spine |
| When to raise | Type is close to the fold | Many sheets or thick stock |
How the tool applies them
Gutter insets each slot on the spine edge. The preview paints a tinted band there. Creep uses δ(i) = totalCreep × i / max(S−1, 1). The outer sheet does not move. The innermost sheet takes the full total. Left pages move right (toward the fold); right pages move left. There is no toward-trim mode.
Bleed is a third control: a uniform inset from the artwork box to trim. Artwork is CropBox if present, else MediaBox. bleed = 0 means that box is trim. The tool does not hunt for printer marks.
A practical starting point
Zine default: 3 mm gutter, no creep. Thick booklet: 5 mm gutter and an 80 gsm estimate for the current sheet count. No creep: all zeros. Then print a test sheet. If the staple bites letters, raise gutter. If the outer pages look tighter at the fore-edge after folding, raise total creep. Estimates are not press guarantees.
Open the booklet creep calculator if you want the GSM helper expanded, or the PDF booklet maker to impose the file.