Your printer just emailed back asking for the artwork as 'PDF/X'. You sent them a perfectly normal PDF, so what's the difference? PDF/X is a print-ready version of PDF — fussier about fonts, colours and bleeds, because professional presses don't get second chances.
Made for the press
PDF/X (ISO 15930) is a stricter sub-format for prepress. It forces every font to be embedded, every colour to be defined precisely (usually in CMYK), and every image to be high resolution. The point is to remove guesswork from the printer's end. When the press starts running, the file must already contain everything needed.
What it strips out
Anything that might confuse a printing press is forbidden: transparency layers (in older versions), JavaScript, external file references, and RGB colour without conversion. Your design software handles the conversion when you export. The result is a leaner, predictable file the printer can trust without having to ring you back.
When you'll need one
Business cards, magazines, packaging, brochures — anything sent to a commercial printer. If you only need office printing, a regular PDF is fine. Either way, you can still merge, reorder pages, or shrink the file with Flint without breaking the print spec.
FAQ
Can I open PDF/X like a normal PDF?
Yes. Any reader opens it. The strictness only matters when the file is going to print — for screen viewing, you'd never notice the difference.
Which version of PDF/X should I send?
Ask your printer. PDF/X-1a is widely accepted for CMYK-only jobs; PDF/X-4 supports transparency and is the modern default. Always confirm before exporting.
Do I need special software to make PDF/X?
Most design tools (InDesign, Illustrator, Affinity, Scribus) export PDF/X directly from their Save or Export menu. You don't need a dedicated converter.
Got a PDF/X file you need to check? Open it in Flint for a quick look, page reorder or merge before sending to print.