♚Packaging

Print-Ready Files Checklist: CMYK vs RGB, Bleed, Resolution, Fonts and PDF/X Explained

By Abdullah Zahoor, ChessCraft Studio · 7 min read

Most print problems are not design problems. They are file problems: a logo that prints dull because it was left in RGB, white slivers along the edge because there was no bleed, a missing font that swaps to something else. Each one costs time, and on packaging runs it can cost an entire print job.

This checklist covers everything we check before artwork leaves the studio, whether it is a business card or a full packaging design on a dieline. Always treat your printer’s own specification as the final word: where it differs from the general guidance below, follow the printer.

Print-ready file specs at a glance

CMYK vs RGB: which colour mode for print?

Screens mix light (red, green and blue). Printing presses mix ink (cyan, magenta, yellow and black). RGB can show brighter, more saturated colours than CMYK ink can reproduce, especially vivid greens, blues, oranges and neons. When an RGB file is converted for print, those colours are pulled back into what ink can achieve, and they often look duller than on screen.

What to do:

• Design print work in CMYK from the start, or convert early so you can see and adjust the shift yourself rather than discover it on the proof.
• Use your printer’s colour profile when converting. Printers in Europe commonly work to FOGRA-based profiles, and many in the US to GRACoL or SWOP. Ask which one they want.
• Keep your brand’s CMYK values in your brand guidelines so every printer starts from the same numbers. Our guide on what to include in brand guidelines covers this.

When to use spot colours

Spot colours (most commonly from the Pantone system) are premixed inks printed as their own colour. Use them when a brand colour must match exactly across runs, when CMYK cannot reach the colour, or for metallic and fluorescent inks. In the file, set them up as named spot swatches that match the Pantone reference exactly, and tell your printer which ones you are using, as each spot colour usually adds a plate and cost to the job.

Getting black right

Small text, thin lines and barcodes should be 100% black (K) only. Built from all four inks, they can look blurry if the plates are even slightly out of register. Large black areas, on the other hand, can look flat and greyish in 100% K, so printers often recommend a rich black. One printer’s published recipe is C40 M30 Y30 K100; ask yours for their preferred mix, and keep total ink within their limit (one UK trade printer, for example, advises not exceeding 300%).

Bleed, trim and safe zone

Printers print on larger sheets and cut them down, and the cut always moves slightly. These three lines protect your design from that movement:

• Trim line: the finished size of the piece.
• Bleed: any colour, image or background that touches the edge must extend beyond the trim, typically 3 mm in the UK and Europe or 0.125 in (about 3.2 mm) in the US. An 85 x 55 mm business card is therefore supplied at 91 x 61 mm.
• Safe zone: keep text, logos and important details well inside the trim, typically 3 to 5 mm.

Set bleed in your document settings (InDesign and Illustrator both have bleed fields) rather than making the artboard bigger, so crop marks are placed correctly on export. Large format and some packaging jobs need more bleed, so check the template.

For packaging, these lines live on the dieline itself. If you have not worked with one before, read what a dieline is and how designers use it.

Resolution: is 300 dpi always necessary?

For most print viewed at arm’s length (packaging, flyers, brochures, cards), images should be 300 ppi at the size they will print. That last part matters: a 300 ppi image scaled up to 200% in your layout is only 150 ppi effective, which may print soft.

• Check the effective resolution in your layout software’s links or document info panel, not just the original file.
• Do not upscale a small web image and call it 300 ppi. The detail is not there.
• Large format (banners, posters seen from distance) can often use lower resolution; your printer will say what they accept.
• Vector artwork (logos, icons, type) has no resolution limit, so keep it vector rather than placing it as a flat image.

Also check your PDF export settings so images are not downsampled below 300 ppi during export.

Fonts, lines and small details

• Embed or outline fonts. A correctly exported PDF/X embeds fonts. Some printers also ask for text converted to outlines. If you outline, keep an editable copy, because outlined text cannot be edited later.
• Minimum line weight: at least 0.25 pt. Hairlines may vanish.
• Small reversed text (white text on a colour) fills in easily. Use a heavier weight and a larger size than you would for dark text on white.
• Barcodes: 100% K on a white or very light background, never scaled below the size your barcode standard allows, and never stretched.
• Flatten or remove form fields in PDFs, as their contents may not print.

Exporting a print-ready PDF: PDF/X-1a or PDF/X-4?

PDF/X is a family of ISO standards for print. The two you will meet most:

• PDF/X-1a is older and strict. Transparency is flattened, and all colour must be CMYK or spot, with RGB converted on export. It is predictable and widely accepted.
• PDF/X-4 keeps transparency and layers live and allows colour-managed RGB and Lab alongside CMYK and spot, leaving the final conversion to the printer’s workflow. Many printers now prefer it.

Some printers ask for other variants (PDF/X-3, for example). The rule is simple: use the preset your printer names, add crop marks and bleed in the export dialogue as they specify, and ask for their export preset file if they have one.

Specifications differ between printers, presses and materials. Always check the printer’s artwork guide or template for bleed, safe zone, colour profile, ink limit and PDF standard before final export.

Spot colours, finishes and dielines

Packaging and premium print often include finishes that are not ink colours: foil, spot UV, embossing, white ink on clear or kraft materials, or varnish. Printers usually need each of these as:

• A separate layer or a named spot colour swatch (for example “Foil” or “SpotUV”), in 100% solid shapes
• Set to overprint so it does not knock out the artwork underneath
• Aligned precisely to the artwork it enhances

The dieline should also be its own named spot colour on its own layer, set to overprint, so it is visible for checking but never printed. For a real packaging project from our studio, see our chocolate gift bag packaging case study.

Checklist: before you send files to print

• Document is the correct trim size, using the printer’s template where provided
• Bleed added on every trimmed edge (3 mm or 0.125 in, or as specified)
• All text and logos inside the safe zone
• Colour mode CMYK, converted with the printer’s profile
• Spot colours named correctly and only where intended
• Small text, thin lines and barcodes in 100% K
• Large black areas in the printer’s rich black, within the ink limit
• Images at 300 ppi effective resolution, no upscaled web images
• Fonts embedded or outlined, editable master file saved
• Lines at least 0.25 pt
• Finishes and dieline on separate named layers, set to overprint
• Exported to the PDF/X standard your printer asks for, with crop marks
• Separations preview checked and a final proof approved

Questions