PDFA1a

PDF/A-1a, often written as PDF/A-1a, is a conformance level of the PDF/A standard for long-term electronic document preservation. It is defined as part of the ISO 19005-1:2005 family and builds on PDF 1.4 to ensure that documents can be reliably rendered and accessed in the future.

The key distinction of PDF/A-1a is its requirement for tagging and structure information. A-level conformance demands that the document is fully tagged (a tagged PDF) with a logical structure, reading order, and other accessibility features. This tagging supports screen readers, text extraction, and automated processing, making PDF/A-1a suitable for accessible archives as well as long-term retrieval.

In addition to tagging, PDF/A-1a enforces constraints to ensure self-containment and reproducibility. All fonts must be embedded, color must be defined with device-independent color spaces or ICC profiles, and the document should not rely on external resources. The file should be free of encryption and scripts, and metadata, often encoded in XMP, should accompany the content. Other forms of external content and dynamic features are restricted to preserve long-term display accuracy.

PDF/A-1a sits alongside PDF/A-1b, where the latter requires faithful visual reproduction but not tagging for accessibility. The PDF/A-1 family has been superseded by later editions (PDF/A-2 and PDF/A-3), but PDF/A-1a remains in use for older archives and systems. The standard is commonly applied by libraries, government agencies, and digital preservation programs, typically validated through conformance checkers.