It has lot of obligation where in non PDF/A has optionable
PDA/A must have or be
Device independent
100% selfcontained
Guaranteed WYSIWIG
Guaranteed color reproduction
Contains XMP metadata
Guaranteed accessibility across mutiple platforms/systems
Embedded fonts
Free from proprietary constraints
Able to capture document' logical structure
All this feature a optionable in normal PDF and not just an option PDF/A
PDF/A add
Archival standard appoved by ISO as a obligation.
PDF/A-2 add
enclosing PDF into the PDF as an option
PDF/A-3 add
enclosing any MIMES extention into the PDF as an option
it's a open source validator
http://verapdf.org/home/type "PDF PDF/A" in google image it's a cuples of copywrited image that are very expressive
Quote:
From wikipedia
PDF/A-1
Part 1 of the standard was first published on September 28, 2005,[2] and specifies two levels of conformance for PDF files:[12]
PDF/A-1b – Level B (basic) conformance
PDF/A-1a – Level A (accessible) conformance
Level B conformance requires only that standards necessary for the reliable reproduction of a document's visual appearance be followed, while Level A conformance includes all Level B requirements in addition to features intended to improve a document's accessibility, such as:
Language specification
Hierarchical document structure
Tagged text spans and descriptive text for images and symbols
Character mappings to Unicode
Level A conformance was intended to increase the accessibility of conforming files for physically impaired users by allowing assistive software, such as screen readers, to more precisely extract and interpret a file's contents.[12] A later standard, PDF/UA, was developed to eliminate what became considered some of PDF/A's shortcomings, replacing many of its general guidelines with more detailed technical specifications.[13]
PDF/A-2
Part 2 of the standard, published on June 20, 2011,[3] addresses some of the new features added with versions 1.5, 1.6 and 1.7 of the PDF Reference. PDF/A-1 files will not necessarily conform to PDF/A-2, and PDF/A-2 compliant files will not necessarily conform to PDF/A-1.
Part 2 of the PDF/A Standard is based on a PDF 1.7 (ISO 32000-1), rather than PDF 1.4 and offers a number of new features:
JPEG 2000 image compression
support for transparency effects and layers
embedding of OpenType fonts
provisions for digital signatures in accordance with the PDF Advanced Electronic Signatures – PAdES standard
the option of embedding PDF/A files to facilitate archiving of sets of documents with a single file.[10]
Part 2 defines three conformance levels. PDF/A-2a and PDF/A-2b correspond to conformance levels a and b in PDF/A-1. A new conformance level, PDF/A-2u, represents Level B conformance (PDF/A-2b) with the additional requirement that all text in the document have Unicode mapping.[12][14]
PDF/A-3
Part 3 of the standard, published on October 15, 2012,[4] differs from PDF/A-2 in only one regard – it allows embedding of arbitrary file formats (such as XML, CSV, CAD, word-processing documents, spreadsheet documents, and others) into PDF/A conforming documents.[15]
PDF/A-4
Part 4 of the standard, based on PDF 2.0, is expected to be published in 2018.