PDF/X is a subset of PDF – see “Technical side and requirements of PDF/X” for an overview. As such, conforming with PDF/X means accepting specific requirements and restrictions to the use of the PDF format.
One principle of PDF/X is that conforming files must be complete, i.e. fully self-contained. In addition, nothing may appear on a PDF/X page that is either not printable at all (such as video or 3D) or where print output is not fully defined (for example, if a font is not embedded). While the first rule is rather easy to implement, the latter is more difficult. PDF allows for many complex situations, for example, colors in semi-transparent overlapping objects. In other cases, it may not be clear whether objects on a layer are to be printed. There are many other cases of interdependencies in which it is difficult to determine whether the print result is unambiguously defined, or not.
Certain features needed only for some print applications (e.g., a bleed zone) are not required in PDF/X as they are not required in all print products. Wherever it makes sense in such cases, however, PDF/X requires that if such information is present, it must be accurate. PDF/X requires, for example, that if a bleed zone is defined then that zone must not be enclosed by the trimmed print product.
These requirements apply in all parts and conformance levels of PDF/X.
PDF/X does not include provisions that although important, may vary depending on the printing conditions, e.g. the minimum image resolution or the bleed zone.
Other non-ISO standards have been developed based on PDF/X that cover such production specific requirements (see “Further quality requirements: PDF/X-Plus” for further information).
Dietrich von Seggern received his degree as a printing engineer, and in 1991 started his professional career as head of desktop prepress production in a reproduction house. He became involved in research projects for digital transmission of print files, and moved to the German Newspaper Marketing Organisation (ZMG). There Dietrich was responsible for a project to enable the digital transmission …