Artwork & File Preparation — Technical Specification Overview

File Format and Colour Space Requirements Across Packaging Print Processes #

Not all packaging print processes accept the same file format or colour space — and submitting the wrong combination is one of the fastest ways to delay a production run. The table below shows what we require at intake for each major process we run.

The data above reflects what our prepress desk actually checks against during what we call the AF-01 intake review — the first-pass file audit every job goes through before it reaches the colour team. Files that fail AF-01 get flagged before they ever reach the planner.

What the table tells you, practically: if your brand uses a single packaging line with multiple print processes (which is common for a brand running a rigid box with an inner folding carton and a flexible inner pouch), your artwork agency needs to export different file versions for each process. A single PDF/X-4 is not a universal delivery format across all five processes above. This is where most multi-SKU launches get delayed: one agency, one export, one format — sent everywhere.

Our stance: we prefer PDF/X-4 for offset work because it supports live transparency and layered spot channels without flattening artefacts. For everything else, PDF/X-1a with pre-flattened output is more predictable across our RIP workflows.

Where Colour Accuracy Breaks Down Between Brief and Press Sheet #

Colour problems in packaging almost never originate at press. By the time a press operator is holding a sheet, three or four decisions upstream have already determined whether the colour will match — or not.

The first failure point is RGB-to-CMYK conversion without a declared output intent. When a brand submits RGB artwork (created in Adobe RGB or sRGB for screen use) without specifying a target CMYK profile, our colour team has to assign one. We default to ISO Coated v2 (FOGRA39) for coated paperboard work and GRACoL 2013 for US-market jobs where the buyer has a G7-certified approval workflow. If the brand intended a saturated lifestyle photo to look vibrant on a gloss-laminated rigid box lid, but the file was built in Adobe RGB and converted to FOGRA39 without gamut mapping, blues and purples will compress noticeably. The conversion happens correctly per the standard — but it doesn’t deliver the brand’s visual intent. We catch this in AF-01 and flag it, but resolving it requires a revised file from the agency, not a press adjustment.

The second failure point is Pantone spot colour naming inconsistencies. We have received files where the same brand colour appears labelled as “PMS 286 C”, “Pantone 286”, “Blue Spot 1”, and “Brand Blue” across different layers of a single document. Each of those names routes to a different ink specification in our RIP. On a job with a hot stamp die and a flood coat on the same carton, that kind of inconsistency will result in two different mixed inks being specified for what should be one colour. Our standard is to normalise all spot names to Pantone’s official notation (e.g., “PANTONE 286 C” with full notation including coated/uncoated suffix) during AF-01, and we document any renaming in the job sheet so the brand can update their master file.

The third failure point is overprint settings on knockout text. Black text set to overprint on a dark background will disappear when printed. White text set to knock out on a CMYK build will show a halo if register tolerance exceeds ±0.2mm, which is our sheet-fed tolerance on a good day. When we run inline camera inspection (100% coverage on our carton lines), we catch register halos at the 0.3mm threshold — but artwork set up incorrectly means the job needs to stop and restart, not just continue with inspection. We require all overprint/knockout settings to be confirmed as intentional in the file handoff notes, not assumed from visual inspection of a PDF preview.

Should Brand Colour Approval Be Done on Screen or Printed Proof? #

Printed proof, always — for anything going to production. Screen-based approval is acceptable for structural dieline review and copy proofing, but not for colour sign-off.

A calibrated monitor running a soft proof under ISO 3664:2009 D50 viewing conditions can get very close to press output, but it cannot account for substrate metamerism, gloss effects on laminated stock, or the optical brightening agents in white board that shift apparent white point. Our standard for brand colour approval is a physical G7-certified inkjet proof on a substrate-representative media, signed off before any plates or cylinders are made. For folding carton jobs, that proof turnaround is typically 2–3 working days from approved file. Rigid box jobs using specialty foil or soft-touch lamination require an additional material-matched proof, which adds another 3–4 working days to the approval cycle.

Specification Notes for Brand Partners #

When you brief us on a new packaging artwork job, the three things that move the project fastest are: a confirmed output profile (tell us whether you’re targeting ISO Coated v2, GRACoL, or SWOP), all spot colour names in full Pantone notation with coated or uncoated suffix specified, and a dieline in a separate locked layer or file.

The most common brief gap we see is artwork supplied at final size without bleed, where the brand assumed we would add bleed during prepress. We cannot add bleed accurately without access to the original layered file — stretching a flattened PDF introduces artefacts at hard-edged design elements. The solution is simple: brief your agency to always supply 3mm bleed on all edges as a non-negotiable export setting.

Our standard sampling timeline for a first physical proof runs 5–7 working days from AF-01 approval. That timeline extends if the file fails intake (add 3–5 days for revision rounds), if the job requires a specialty proof substrate, or if colour approval requires multiple rounds. Jobs with pre-approved master artwork templates typically run 3–4 working days to first proof. Supplying an accurate, complete brief file is the single variable most within your control.

Frequently Asked Questions #

What resolution do we actually need for packaging artwork — is 300 dpi always sufficient?

It depends on the print process and viewing distance. For sheet-fed offset cartons viewed at arm’s length, 300 dpi at final size is sufficient for photographic content. For fine line detail in flexo or gravure (think small-point legal text or thin decorative borders), we recommend supplying text and vector elements as pure vectors regardless of the surrounding raster resolution — rasterised fine lines at 300 dpi will not hold cleanly on a 150 lpi flexo screen. Bitmap elements like barcodes and QR codes must be supplied at 1200 dpi minimum or, preferably, as vector EPS.

Can we submit layered InDesign or Illustrator native files instead of PDF?

We accept native AI and INDD files under specific conditions, but PDF/X is strongly preferred. Native files require our team to verify font licensing, linked image paths, and live effect rendering — all of which add time to AF-01 and introduce variables our RIP workflow does not face with a properly exported PDF. If you send a native file, all fonts must be outlined or embedded, all linked images must be supplied at print resolution in a collected package, and any live effects must be flagged. For urgent jobs, a clean PDF/X-4 will always process faster.

Does UGI accept files with RGB images if we convert them on our end before sending?

Yes, but the conversion method matters more than who performs it. A file converted from sRGB to CMYK using Photoshop’s default settings without a declared output intent profile will be interpreted differently by our RIP than a file converted with a named ISO Coated v2 profile and relative colorimetric rendering intent. When you convert on your end, embed the output intent in the PDF and tell us which profile was used in the file handoff notes. That way our colour team validates against your intent, not against an assumed default.

Planning a packaging project? Contact our team to request a complimentary specification review and sample quote.