Preparing Print-Ready Files: CMYK, Bleed and 10 Mistakes That Ruin a Print Run

For artwork to print as intended, the file must be in CMYK (or with Pantone colours specified), include bleed — usually 3 mm on each side — use images at around 300 dpi at final print size, have fonts outlined or embedded, and keep important text inside a safe zone. Export to PDF according to your printer's requirements, most often PDF/X-1a or PDF/X-4.

Why colours look different on screen and on paper

A screen creates colour with light (the RGB model), while a printer uses ink on paper (the CMYK model: cyan, magenta, yellow, black). Many bright colours that are easy on screen — neon green, saturated blue, vivid orange — simply cannot be reproduced in CMYK. If you send an RGB file, the printer will convert it automatically and colours will become duller or shift.

• Work in CMYK from the start if the design is meant for print.
• Ask the printer which ICC colour profile to use: coated and uncoated papers need different profiles.
• For brand colours that must match from run to run, use Pantone — but only if the printer runs an extra spot ink.

Bleed, trim and the safe zone

Printers print on a larger sheet and then cut it. The blade can drift by 1–2 mm, so:

• Bleed — backgrounds and images that touch the edge must extend beyond the trim line, usually by 3 mm (5 mm for some products). Otherwise a white sliver remains after cutting.
• Safe zone — keep text, logos and key elements at least 3–5 mm inside the trim line so they are not cut off.
• Spine and gutter — for saddle-stitched and perfect-bound catalogues, remember that part of each spread disappears into the binding.

Image resolution

For quality offset printing, images should be about 300 dpi at their actual size on the page. A web image 800 pixels wide placed on an A4 page will look blurry and pixelated. Upscaling in Photoshop does not add detail — you need a better source file. Large-format printing (banners, billboards) has lower requirements because it is viewed from a distance; check with your supplier.

A printer prints your file, not your intentions. Anything not built into the artwork — colour, bleed, resolution — will not appear on paper.

10 mistakes that most often ruin a print run

1. The file is in RGB — colours become duller after conversion.
2. No bleed — white edges after trimming.
3. Text too close to the edge — it gets trimmed or looks cramped against the cut.
4. Low-resolution photos — blurriness and pixelation.
5. Fonts neither outlined nor embedded — the printer substitutes another font and the layout breaks.
6. Small text in four-colour black — any misregistration makes it fuzzy. Small black text should be 100% K only.
7. Total ink coverage too high — dark fills above the paper's ink limit dry slowly, set off and stick together. Ask your printer for the limit.
8. Hairlines and small reversed text — white text smaller than 6–7 pt on a dark background can fill in with ink.
9. Wrong black for large areas — 100% K over a large area looks grey; a rich black recipe recommended by the printer gives deep black.
10. Finishing not planned — lamination, spot varnish, foil and die-cutting require separate layers or files that must be prepared in advance.

File format for the printer

Most printers accept PDF. The best option is a PDF/X export (X-1a or X-4 — check with your printer) with crop marks and bleed. Packaging additionally needs the dieline on a separate layer or as a non-printing spot colour. Multi-page products such as catalogues are usually sent as one PDF with single pages (not spreads), unless the printer asks otherwise.

Exporting a print PDF step by step

The workflow in InDesign or Illustrator is almost the same. If you follow it every time, most errors are caught before the file is sent:

1. Check the document size. It must match the trimmed size of the product, not the sheet size.
2. Set bleed in the document settings and make sure backgrounds and photos actually extend into it.
3. Check linked images. The Links panel should show no missing or modified files, and effective resolution should be sufficient.
4. Run Preflight with a profile that flags RGB, low resolution and missing fonts.
5. Export with the PDF/X preset your printer recommends, with crop marks and bleed enabled.
6. Open the final PDF in Acrobat and use Output Preview: check separations, total ink coverage and any stray spot colours.
7. Check overprint. A white object set to overprint will disappear in print, while black text usually should overprint.

How preparation differs by product

• Business cards and flyers. Small formats make the safe zone and small text especially critical. They are often printed digitally — ask whether PDF/X is needed or a regular high-quality PDF will do.
• Catalogues and brochures. Binding type matters, as does page count (a multiple of four for saddle stitching), creep compensation for inner pages and consistent styles throughout.
• Packaging and labels. The dieline on a separate layer, flaps and glue areas, board grain direction, zones for barcodes and marking codes. They are often printed flexographically, which has its own rules for dot gain and minimum line weight.
• Outdoor advertising. Files are often built at reduced scale, and resolution and bleed requirements depend heavily on the supplier and material.

If you are not sure which category your job falls into, or the product combines several finishing processes, send the printer a sketch or a photo of a similar sample before layout begins. Their prepress specialist will tell you which layers and separate files are needed, which saves you from reworking the design at the last stage when deadlines are already tight.

Working with your printer

Most print problems can be prevented with one conversation before layout begins. Ask the printer for written technical specifications: file format, colour profile, bleed, total ink limit, dieline and finishing requirements. If they are not published, the printer's account manager will usually send them on request.

• Share the run length, paper and print method in advance — file settings depend on them.
• Ask for a file check before printing: many printers offer a free technical preflight.
• Agree who is responsible for errors if the printer makes changes to the file.

Proofs

If colour is critical — a brand colour, packaging, product photography — order a contract proof or press proof. It costs far less than reprinting a run. Also bear in mind that the same image looks different on coated, uncoated and kraft paper: colours are always more muted on uncoated stock.

Checklist before sending files to print

• CMYK colour mode, the right ICC profile, Pantone colours specified separately.
• 3 mm bleed (or per printer requirements) on all sides.
• Important elements no closer than 3–5 mm to the trim.
• Images at around 300 dpi at print size.
• Fonts outlined or embedded in the PDF.
• Small black text set as 100% K only.
• Total ink coverage within the printer's limit.
• Varnish, foil and die-cut on separate layers or files.
• File checked with Preflight (Acrobat or InDesign).
• Printer requirements obtained and followed before export.

At Dasta Creative we prepare print-ready files as part of every catalogue design and packaging project, and where needed we agree technical requirements with the printer ourselves.