Bleed, Trim Margin & Safe Area Guide

1. Three rectangles: bleed line · trim line · safe area

A printed piece is produced on oversized paper then trimmed to finished size. Because guillotines have a ±0.5–1mm tolerance, three boundaries absorb that variation.

• Bleed line — outside the trim. Backgrounds/images must extend to here so trim variance doesn't leave a white edge. Standard: 3mm.
• Trim line — the finished size. Where the cutter hits.
• Safe area — inside the trim. Logos, text, and critical content must stay within this margin to survive trim variance. Typically 3–5mm.

2. Korean print shop bleed standards

Requirements vary 1–3mm between shops. Always check your vendor's "submission guide" PDF before ordering.

3. Resolution: why 300dpi is the print standard

The human eye can't resolve finer detail than ~300dpi at 25cm. Print material is viewed at roughly that distance, so more than 300dpi yields little visible improvement while less reveals pixels.

• 72dpi — screen-only. Unacceptable for print.
• 150dpi — minimum for large posters viewed from a distance.
• 300dpi — print standard for business cards, flyers, booklets.
• 600dpi — fine-art books and highly detailed halftone work.

Formula: 210mm × 300dpi ÷ 25.4mm/inch ≈ 2480px (A4 width).

4. Brochure folds: 2-panel, 3-panel, gate-fold

• Half-fold (2-panel) — one center crease, 4 pages.
• Tri-fold (roll fold) — inner panel (~2mm narrower) tucks under the outer panels. Inner width ≈ total/3 − 2mm.
• Z-fold (accordion) — all three panels equal width; folds in alternating directions.
• Gate-fold — left and right flaps each half the center width, opening outward.
• Booklet spread — facing pages printed as one sheet; keep critical content 5mm clear of the spine crease.

5. CMYK · RGB · K100

• Presses print in CMYK ink. RGB originals are converted at output — expect color shifts, especially in saturated hues.
• Black text should be set to K100 (C0 M0 Y0 K100) to avoid color fringing from four-plate misregistration.
• Large black fills: use rich black (C40 M30 Y30 K100) for deeper density.

6. File formats

• PDF/X-1a — industry print-exchange standard. Requires CMYK, embedded fonts, bleed marks.
• AI (CS6 or lower) — some older presses require this; convert all text to outlines.
• TIFF/PNG — save at 300dpi + CMYK.

7. Pre-flight checklist

1. Create document at bleed size (finished + bleed × 2).
2. Extend backgrounds to the bleed line.
3. Keep critical content inside the safe area.
4. Minimum 300dpi (150dpi acceptable for large-format posters).
5. CMYK color mode; black text at K100.
6. Outline fonts or embed them.
7. Export as PDF/X-1a; verify against the shop's spec sheet.