add-bleed

name	add-bleed
description	Add bleed margins to a PDF for commercial print shops that trim — extends the page size by the bleed amount on each side and shifts content to the new center. Most office digital printing does NOT need this; use only when sending to a print shop. Triggers on phrases like "add bleed", "add 3mm bleed", "prep for trim".

Add Bleed

Expand a PDF's page size to add bleed on every side. Commercial print shops trim to the trim line; the bleed area absorbs registration error.

When to use

• Sending to a commercial / offset / print-shop digital press that trims final size.
• Document has edge-to-edge images or color that should extend past the trim.

When NOT to use

• Office laser/inkjet printing — these don't trim, and printing onto a larger page just wastes paper or fails.
• Standard documents with white margins — bleed adds nothing.

Inputs

• Input PDF path (required).
• Bleed amount (optional, mm) — default 3mm (industry standard). Some shops want 5mm.
• Output path (optional) — defaults to <input>-bleed.pdf.

Tooling

pdfjam or ghostscript. Strategy: increase MediaBox by 2 × bleed on each axis, then shift content by bleed so it remains centered.

Recipe (ghostscript)

# input is A4: 595 x 842 pt; 3mm = 8.5 pt
gs -o output.pdf \
   -sDEVICE=pdfwrite \
   -dDEVICEWIDTHPOINTS=612 \
   -dDEVICEHEIGHTPOINTS=859 \
   -dFIXEDMEDIA \
   -c "<</PageOffset [8.5 8.5]>> setpagedevice" \
   -f input.pdf

Caveats

• This skill does not extend background images/colors into the bleed area — it just adds whitespace. If the source layout has edge-to-edge images, those need to be redesigned with bleed at the source (Indesign, Affinity, etc.). Adding bleed after the fact on an already-laid-out PDF leaves a visible white band around content.
• For source-correct bleed, redo layout with bleed enabled in the design tool. This skill is a last-resort prep.

Output

Bleed-extended PDF.