Print production and PDF/X-4 — since 1.7.0, CMYK in 1.8.0

Bleed boxes and printer's marks since 1.7.0; since 1.8.0, CMYK colours, CMYK OutputIntents, marks in the registration colour, a PDF/X-4 conformance claim and validatePdfX(). The CMYK-intent presets take an output ICC profile. Choose the one your printer names (ISO Coated v2, GRACoL, SWOP…) — the file is read in your browser and never uploaded — or choose none and the page falls back to the synthetic CMYK profile inlined below, the same one the repository's samples use. The synthetic profile is structurally complete (a prtr profile validators accept) but characterises no press: a real job needs your printer's profile. pdfnative itself ships none.

Preset: ICC profile (optional): Colour bars (5 mm bleed) Claim PDF/A-2b under the default sRGB intent (CMYK preset → PDFA_DEVICE_CMYK_CONTENT)

View underlying code

Diagnostics (layout.onDiagnostic)

Generate a PDF to see the diagnostics its build raised. Every preset wires layout.onDiagnostic; a coherent print job raises none. Tick the PDF/A-2b claim on the CMYK preset to see PDFA_DEVICE_CMYK_CONTENT: CMYK colour under a claim whose OutputIntent is not CMYK.

Worth knowing:

The synthetic profile is built by scripts/lib/synthetic-cmyk-profile.ts in the repository: an ICC v2 output profile (prtr, CMYK data, Lab connection space) with a naive device transform. It exists so that samples and this page can be self-sufficient; it describes no printing condition, so never send a file built with it to a press.
CMYK colours are [c, m, y, k] in percent, or a 'C M Y K' string in 0–1; they are written with k / K.
Under a CMYK intent, the RGB colours pdfnative draws by default are remapped through a calibrated /DefaultRGB, so the PDF/A or PDF/X claim holds.
PDF/X-4 rejects, before writing, a PDF/A level, encryption, a missing or non-output profile, and trapped: 'Unknown'.
validatePdfX() checks the structure; veraPDF does not cover PDF/X, so confirm press files with a certified preflight.
Colour bars (marks: { colourBars: true }) paint C, M, Y, K at 100 % and 50 % in the bottom bleed strip as DeviceCMYK fills. They need a 5 mm bleed to reach the 12 pt default patch — 3 mm would clamp them to 7.5 pt — and a CMYK intent under PDF/A or PDF/X.

See the Print production guide for the full options.