Print-Ready Files Explained: CMYK, Bleed, 300 DPI and Safe Zones

A plain-English guide to preparing print-ready files: RGB vs CMYK, resolution and DPI, bleed and trim, safe zones, fonts and export settings, so your posters, flyers and zines print the way they look on screen.

You design something that looks perfect on screen. You send it to print. It comes back with dull colours, a white sliver on one edge and the text slightly too close to the trim.

Almost every print disappointment comes down to the same handful of settings. This guide explains them in plain English.

1. RGB vs CMYK

RGB (red, green, blue) is how screens make colour with light.
CMYK (cyan, magenta, yellow, black) is how most printers make colour with ink.

Screens can show colours ink can't reproduce, especially bright greens, electric blues and neon pinks. When those are converted to CMYK, they get duller.

What to do:

Ask your printer whether they want RGB or CMYK files. Many digital printers accept RGB and convert themselves; offset printers usually want CMYK.
Preview in CMYK before you send, so you aren't surprised.
If you need neon or very bright colours, look at spot colours or risograph printing, which use specific inks.

2. Resolution and DPI

DPI (dots per inch) or PPI (pixels per inch) describes how much detail is packed into each printed inch.

300 DPI at final size is the standard for anything viewed up close: flyers, books, cards.
150 DPI is often fine for large posters viewed from a distance.
72 DPI is a screen convention and too low for print.

The maths: an A4 page is about 8.3 × 11.7 inches. At 300 DPI that's roughly 2480 × 3508 pixels.

You can't add real detail by upscaling a small image. Start with large enough source files.

3. Bleed

Printers print on bigger sheets and then cut them down. The cut is never perfectly exact. If your background colour stops exactly at the edge, a slight shift leaves a white line.

Bleed is extra artwork that extends past the trim line, so the cut lands inside the colour.

Common bleed: 3 mm (or 0.125 in in the US).
Extend backgrounds and edge images into the bleed.
Check your printer's spec. Some want 5 mm for larger formats.

4. Trim and safe zone

Trim line: where the paper is cut.
Safe zone: an inner margin, often 3–5 mm inside the trim, where all important content should stay.

Keep text, logos and faces inside the safe zone. Anything between the safe zone and trim might get cut.

5. Black isn't just black

In CMYK:

100% K (plain black) is great for small text. It stays crisp.
Rich black (black plus some C, M and Y) looks deeper for large solid areas.

Don't use rich black on small text; slight misalignment between inks makes it blurry.

6. Fonts and outlines

If the printer doesn't have your font, the file may print with a substitute. Either embed fonts in the PDF or convert text to outlines before sending.

7. Export settings

For most jobs, a PDF is what printers want:

Fonts embedded
Images at 300 DPI at final size
Bleed included
Crop marks if the printer asks for them

For riso and screen printing, printers usually want one greyscale file per ink instead.

Doing this in Bitgrain

Bitgrain is built with print output in mind:

Multi-page PDF export for posters, zines and booklets
True CMYK halftone separations
Risograph exports with one PNG per ink in a ZIP
Screen-print-ready limited palettes
Pen-plotter SVG with vector paths
SVG export for vector work

Pre-flight checklist

Correct colour mode for your printer

Images at 300 DPI at final size (150 for big posters)

Bleed added (usually 3 mm)

Important content inside the safe zone

100% K for small text

Fonts embedded or outlined

Exported as PDF, or per-ink files for riso/screen print

Final thoughts

Print feels technical, but it comes down to a few rules. Get colour mode, resolution, bleed and safe zones right and most problems disappear.

Next time you lay out a poster or zine in Bitgrain, run through the checklist above before you hit export.