IsTagged property

IsTagged returns True when the document catalog references a /StructTreeRoot — the root of the PDF logical structure tree (PDF 1.7 spec section 14.7). Tagged PDFs encode the document’s reading order, heading levels, table structure, lists, alt-text on images, and other semantic markup that screen readers, reflow engines, and content extractors rely on. PDF/UA-1 and PDF/A-2a/3a conformance both require tagged PDF.

The property is False when Active is False, when no structure tree is declared, or when the structure tree is present but empty. Many PDFs in the wild are not tagged — especially scanned documents, print-driver output, and tool exports from before 2010. Tagged-PDF support in authoring tools is improving but still uneven.

IsTagged is a cheap header check, suitable for routing decisions: skip structure-tree extraction on untagged files (it will simply return empty arrays), or surface an accessibility warning to the operator. The detailed tree is available through StructureElements, which materialises the tree into a flat array of TPdfStructureElement records with level, parent index, type name and role.

• PDFs marked as tagged may still lack alt-text on images or skip heading levels — IsTagged is a structural test, not a quality test.
• Combine with Language (/Lang) to perform the two minimum-viable PDF/UA checks before validating with a full conformance tool.
• Reading IsTagged does not parse the tree itself; it merely checks the catalog for the presence of /StructTreeRoot.