PDF/A-2 was released by ISO in July 2011. PDF/A-1 files are compliant archive documents and do not need to be converted to the new standard. PDF/A-2 does not replace the PDF/A-1 standard.
So, what is the difference between these two standards you might ask.
PDF/A-1 is based on PDF version 1.4 (based on Adobe PDF specifications).
PDF/A-2 is based on the ISO standard 32000-1 and takes advantage of features that came after the Adobe PDF 1.4 specification.
What is new in PDF/A-2:
- JPEG2000 compression (benefits for scanned color documents)
- Embedded PDF/A files via collections/portfolios
- Transparency
- Optional content (layers): useful for mapping or engineering drawings or documents with multiple languages (implement different content on different layers)
- Unicode support (PDF/A-2U)
- Object level XMP metadata (new requirements for custom metadata)
- Comments and annotations (defined list of acceptable and prohibited annotation and comment types for PDF/A-2)
- Digital signature rules defined.
Read more about PDF Standards here.