How to prepare artwork for print: a 10-point checklist

1. Colour mode: CMYK, not RGB

Screens make colour from red, green and blue light. Presses make it from cyan, magenta, yellow and black ink. The two systems do not cover the same range: RGB can show vivid greens, oranges and blues that no combination of four inks can reproduce. When an RGB file is converted at the press, those colours are pulled to the nearest printable equivalent — and “the colour changed” is the complaint that follows.

Before: a bright electric blue on screen prints as a duller purple-blue, and nobody signed off on purple-blue. After: the document is set to CMYK from the start, so what you see is already inside the range the press can print, and the proof matches the screen far more closely.

2. Bleed: 3 mm past the trim on every edge

Cutting is accurate to well under a millimetre, but not to zero. Any colour or image meant to reach the edge of the finished piece must extend 3 mm beyond the trim line, so that a cut landing fractionally wide still lands on ink.

Before: a business card with a coloured background and no bleed shows a hairline of white paper along one or two edges — visible on every card, on the side where the knife landed. After: with bleed supplied in the file, the same variation falls inside printed area and is invisible. Do not fake bleed by scaling the finished design up a few per cent: on a packaging job it will no longer fit the dieline.

3. Safety margin: keep type away from the edge

The mirror of bleed. Just as cutting can land slightly outside the trim, it can land slightly inside — so text, logos and anything that would look wrong clipped must stay a few millimetres in from the trim line. On packaging the margin must also respect creases, because type that crosses a fold is distorted by it.

Before: a footer line sitting 1 mm from the edge loses the bottom of its descenders on a fraction of the run. After: the same line sits inside a safety margin and survives any normal cutting variation. Corners of cartons are where this most often goes wrong: crease, cut and corner radius all take space from the same area.

4. Resolution: 300 dpi at final size

Resolution only means something at a size. An image that is 300 dpi at 50 mm wide is 75 dpi once scaled to 200 mm, and it will print soft. The check is not what the file says in its metadata but what the effective resolution is at the dimensions it will actually print.

Before: a product photo pulled from a website at screen resolution and scaled up looks fine on a monitor and prints as a blur of square pixels. After: the original high-resolution photograph is placed at final size and holds detail down to the grain of the board. If you do not have a high-resolution original, say so — a smaller, sharp image beats a larger, soft one.

5. Fonts: outlined or embedded

A font that lives on your computer does not live on ours. If a file references a font that is not embedded in it, the RIP substitutes something else — and the substitution is rarely announced and never flattering. Either convert text to outlines before export, or make sure the export embeds every font used.

Before: a headline set in your brand typeface prints in a default serif, and the line breaks have moved because the widths differ. After: outlined text is pure shapes and cannot change. Keep an editable copy of the file for yourself, because outlined text cannot be edited later.

6. Black text: 100% K, not four-colour black

Small black text should be built from black ink alone — 100% K, with zero cyan, magenta and yellow. Text built from all four inks has to register four plates perfectly on every letter; any movement at all shows as coloured fringes and the type looks fuzzy.

Before: body copy set in a “black” that is actually 60/40/40/100 prints with a faint magenta or cyan halo, most visible at small sizes. After: the same copy at 0/0/0/100 prints crisp from one plate. The exception is large solid black areas, which is the next point.

7. Rich black: for large solids only

Black ink alone is not as dark as it looks on screen. Over a large solid area it reads as a slightly warm dark grey, and next to a photograph with deep shadows it looks weak. For big solid areas — a cover, a background panel — a rich black adds some cyan, magenta and yellow under the black to deepen it.

Before: a full-bleed black cover panel at 100% K looks flat and slightly brown beside the black in the photograph on it. After: the panel uses a rich black and the two match. Use it for solids, never for text, and ask us for the build we recommend for the board — total ink coverage has a limit that varies by substrate.

8. Spot colours: name them, and only where they are needed

Where a brand colour must be exact, define it as a named spot colour — a Pantone reference — rather than a CMYK build. A spot is a separate ink mixed to that colour, so it reproduces exactly and consistently. But every spot is another plate, so a file that accidentally carries five spot colours because five swatches were imported from somewhere is five plates you did not mean to pay for.

Before: preflight reports seven inks on a job quoted as four-colour. After: the swatch panel contains exactly CMYK plus the one Pantone the brand actually uses, and everything else is converted. Check the separations preview before you export — it takes ten seconds.

9. Overprint and knockout: set deliberately

When one colour sits on top of another, the file has to say whether the top colour prints over the one beneath (overprint) or punches a hole in it (knockout). Black text over a colour is normally set to overprint so that slight misregistration never shows a white edge. Anything else set to overprint by accident either disappears or changes colour where it overlaps.

Before: a white logo set to overprint vanishes entirely on press, because white ink over a colour prints as nothing. After: the logo is set to knock out and appears as intended. Turn on overprint preview in your design application before exporting; it shows you what the press will actually do. Our glossary entry goes deeper.

10. The dieline: a separate, non-printing layer

For packaging, the dieline — cut, crease and glue lines — must be in the file so the artwork can be checked against it, and must NOT print. It goes on its own layer, in a named spot colour set to overprint and marked non-printing, with cuts, creases and perforations distinguishable from one another.

Before: the magenta dieline is on the artwork layer and prints as a thin pink outline around every panel of ten thousand cartons. After: the dieline is on its own layer and the artwork registers to it exactly, with bleed extended past every cut and nothing critical crossing a crease. Our dieline templates come set up this way.

And then: export as PDF/X and send it

Export a PDF/X-1a or PDF/X-4 — the print-specific PDF standards, which force fonts to embed, flatten or preserve transparency correctly and lock the colour space. Native application files are fine too, but a PDF/X is the format least likely to behave differently on our system than on yours.

Then send it, even if you are unsure about a point above. Preflight will tell you what is missing, and finding out at that stage costs nothing. The full specification, including file naming and how to send large files, is in our artwork guidelines, with a printable checklist.