Basic Introduction to PDF/X
The PDF/X standard responds to the challenge of ensuring that graphic arts files are written in a way that will reproduce on press exactly as the files' creators intended. As a subset of the Adobe PDF specification, PDF/X is designed for the blind exchange of final print-ready pages, and is one of the most predictable ways to deliver files bound for press.
Using PDF/X-compliant files eliminates the most common errors in file preparation: fonts that aren' t embedded, incorrect color spaces, missing images, and overprinting and trapping issues. These issues don't arise with PDF/X files because, by definition, these standards require that all fonts be embedded, appropriate PDF bounding boxes be specified, and color be correctly and consistently defined. PDF/X-compliant files also must describe the printing condition for which they are prepared.
PDF/X has three variants, PDF/X-1a, PDF/X-3, and PDF/X-4. PDF/X-1a and PDF/X-3 are the most popular PDF/X formats; PDF/X-4 is a new standard, which is expected to be ratified as a CGATS (Committee for Graphic Arts Technologies Standards) and ISO standard in 2007. Click here to learn more details about PDF/X Variants>>
About PDF/X file contents
PDF/X files require certain contents, prohibit others, and leave some open. It's helpful to know what's allowed and prohibited in PDF/X files before creating, preflighting, and correcting them; and when customizing any settings.
Here's what must be included in a PDF/X file:
- Fonts and images embedded.
- Page geometry (the trim box and bleed box) defined.
- Intended printing condition (output intent).
- Trapping key (Yes = True, No = False) defined.
- Title, creator, producer, creation, and modification dates.
Here's what's prohibited in PDF/X files:
- Live transparency, except in PDF/X-4 files.
- Layers, except in PDF/X-4 files.
- Encryption (security).
- Form fields.
- Interactive elements including movies, sounds, buttons, and hyperlinks.
- Annotations within the bleed box.
- Preseparated PDFs.
- Transfer functions.
- Embedded PostScript®.
- PDF/X files do not set a minimum image resolution nor limit the plates used.