A pre-flight checklist before you send to the printer

Preflight is the last pass before you hand a file off: five quiet minutes that catch the mistakes a reprint is made of. Popcorn Editor automates part of it — the Print checks panel in the export flow flags low-res images, spot-color trouble and heavy ink — but a human eye still catches the rest. Here's the full 10-point list to run on any design before you export.

Why preflight beats a proof#

A press operator can't see your intent — only your file. If a background stops at the trim line, they print the white sliver. If an image is 180 PPI, they print it soft. If a foil plate is named wrong, it separates wrong. Every one of those is invisible until the proof comes back, and by then you've lost a day. Catching them on the canvas costs minutes.

Work through the list top to bottom. Most items map to something the app already shows you.

The 10-point checklist#

1. Correct color mode#

Confirm the document's Color mode is set to CMYK (print), not RGB (screen). Press inks are CMYK, and a CMYK document soft-proofs your colors on screen so what you see is close to what the press lays down. While you're there, scan for any too-bright color flagged Outside the CMYK print gamut in Properties — those will look duller in print than on your monitor. Fix or accept them now, not on the proof. (See RGB vs CMYK for the why.)

2. Bleed set and actually filled#

Bleed is art that runs past the trim so the cut never leaves a white edge. Two halves to check: it's set — open File → Document setup… and confirm your bleed (usually 3 mm) — and it's filled — turn on Show bleed and make sure every background, color block and full-bleed photo runs all the way to the red guide, not just to the trim.

A bleed value with nothing extended into it does nothing. The art has to reach the red line.

3. Content inside the safe margin#

Pull text, logos, prices and anything you can't afford to lose about 3–4 mm inside the trim. Presses drift by roughly a millimeter as they cut through a stack, so anything hugging the edge risks being clipped. There's no dedicated safe-area toggle — hold the margin by eye, or drop a guide to keep yourself honest.

4. Images at 300 PPI#

In a CMYK document the editor computes each image's effective PPI — pixels divided by the size it's actually printed at — and warns right on the image when it drops too low: Below recommended print resolution (amber, under 300) or Resolution too low for print (red, well under). The detail reads "{ppi} PPI — 300 PPI recommended." Clear the reds. Scaling an image up on the canvas spreads its pixels thinner, so shrink it, swap in a larger source, or regenerate it — don't upscale a small JPEG. Choosing the right resolution for print goes deeper.

5. Spot colors named and correct#

If your job uses foil, white ink, spot UV, a varnish or a cut line, each lives on its own Spot swatch — a named separation the press treats as its own plate. Confirm each one uses the right Purpose preset (Die cut, White ink, Foil, Spot UV, and so on) and the exact name your printer specified; matching is case-sensitive. Watch for the warnings about names that differ only by case, or a spot name that collides with a process ink. And check that no spot is flagged as lost or rasterized in the export checks.

6. Overprint on technical inks#

Technical inks — die lines, varnish, white underprint — should overprint so they mark the sheet without knocking a hole in the artwork beneath them. The Purpose presets set this, but verify it, and leave Overprint / rich black on at export. Get this wrong and your cut line punches a white gap through your design. See Marks, overprint & rich black.

7. Fonts handled#

At export you choose how text is written into the PDF. Outline text (the safe default) converts every character to vector outlines — RIP-safe, with no font to go missing at the printer. Editable text (best effort) keeps text selectable in Illustrator or InDesign but spacing is approximate and some effects flatten. Pick outlines unless your printer explicitly asks for editable text. An outline can't be substituted with the wrong font on their end.

8. Ink coverage sane#

Watch for heavy, saturated areas — deep four-color blacks, dark photos, rich shadows. Most presses cap total ink coverage near 300%, and the app will warn you: "High ink coverage ({pct}%). Most presses cap total ink near 300%." Overloaded ink doesn't dry cleanly and can set off on the sheet behind it. Build rich black from a recipe your printer recommends rather than piling on all four plates.

9. Right size and count#

Confirm the trim dimensions are genuinely what you ordered — it's easy to design a card at the wrong size. Then, in the Export dialog, make sure the intended canvas (or canvases) are the ones selected. If you're exporting several, decide between a single multi-page PDF and separate files. A perfect file at the wrong size still bounces.

10. Read the Print checks, then export#

Open Share → Download to bring up the Export design dialog and, with Print (CMYK) selected, review the Print checks panel. It aggregates everything above — low-res images, spot-color issues, ink warnings — into one list. It's informational and never blocks your export, so the discipline is on you: clear every red before you click Export print PDF. The RIP runs in your browser (you'll see Generating print PDF…), then the file downloads — no upload, no server round-trip.

The one item the app can't check: your printer's spec#

Every print service has its own house rules — a preferred output profile (FOGRA39 in Europe, SWOP or GRACoL in the US), a specific bleed amount, whether they want crop and registration marks, and how they want files named. The checklist above gets your file technically clean; the printer's spec sheet tells you which settings to clean it to. When anything is ambiguous, one email to your printer beats one reprint.

Keep this list next to your monitor. Run it every time and the "can you resend that?" email stops arriving.

Ready to hand it off? Walk through the settings sheet in How to export a print-ready PDF, or read the reference on Preflight: the print checks for what each warning means and how to clear it.