About PDF/X standards
PDF/X
standards are defined by the International Organization for Standardization
(ISO). PDF/X standards apply to graphic content exchange. During
PDF conversion, the file that is being processed is checked against
the specified standard. If the PDF will not meet the selected ISO
standard, a message appears, asking you to choose between canceling
the conversion or going ahead with the creation of a non-compliant
file. The most widely used standards for a print publishing workflow
are several PDF/X formats: PDF/X‑1a, PDF/X‑3, and (in 2007) PDF/X-4.