Adobe LiveCycle Output ES2 lets you generate PDF documents conforming to the PDF/A (archive) ISO (International Organization for Standardization) document archival standard. Other ISO PDF standards such as PDF/X (graphic arts), PDF/E (engineering) and PDF/UA (accessibility) are not supported by Output ES2.
PDF/A has “Revision Numbers” (1 and 2) and each Revision Number can have “Conformance Levels” (“a” for advanced, “b” for basic and “u” for unicode). Revision Number “2” is not supported by Output ES2.
More information on PDF/A standards are available at the PDF/A Competence Center.