PDF/A is a file format for the long-term archiving of electronic documents. It is based on the PDF Reference Version 1.4 from Adobe Systems Inc. (implemented in Adobe Acrobat 5 and latest versions) and is defined by ISO 19005-1:2005, an ISO Standard that was published on October 1, 2005: "Document Management - Electronic document file format for long term preservation - Part 1: Use of PDF 1.4 (PDF/A-1)".
PDF/A is a file format for the long-term archiving of electronic documents. It is based on the PDF Reference Version 1.4 from Adobe Systems Inc. (implemented in Adobe Acrobat 5 and latest versions) and is defined by ISO 19005-1:2005, an ISO Standard that was published on October 1, 2005: "Document Management - Electronic document file format for long term preservation - Part 1: Use of PDF 1.4 (PDF/A-1)". A new version of PDF/A based on PDF 1.7 - ISO 32000-1 is currently under development (ISO/DIS 19005-2). PDF/A is in fact a subset of PDF, obtained by leaving out PDF features not suited to long-term archiving. For more details, you may browse PDF Standards - PDF/A.
PDF/A is also popular as ePDF format and is accessible through Adobe Digital Editions on most eBooks Reading Systems.