Keywords property

Keywords returns the /Keywords entry from the document Information dictionary (PDF 1.7 spec section 14.3.3). The value is a free-form text string written by the authoring tool and is conventionally a comma- or semicolon-separated list of tags — e.g. "invoice; 2024; payable; vendor-acme". PDF leaves the delimiter unspecified, so applications must accept whatever format the producer wrote (comma, semicolon, line break, or space-separated).

The return value is decoded UTF-16; CJK and other non-ASCII keywords round-trip correctly. The string is empty when Active is False, when the Info dictionary is missing, or when no /Keywords was assigned. Many modern authoring tools also mirror keywords into XMP metadata under pdf:Keywords or dc:subject (a Bag of RDF literals); when both are present they should agree but may diverge after edits.

Keywords are surfaced by desktop search indexers (Windows Explorer, Spotlight, Adobe Bridge) and by most document-management systems. PDFiumVCL exposes the Info-dictionary copy only — access MetaText['Keywords'] for the same value through PDFium’s generic metadata accessor.

• This property is read-only; to set keywords, call FPDF_SetMetaText directly with the “Keywords” tag.
• Some indexing pipelines lower-case keywords for matching — PDFiumVCL preserves casing verbatim. Apply whatever normalisation your search layer requires after reading the string.
• Use the value as informational metadata only; PDF does not restrict the keyword length or content, so treat it as untrusted text when displaying.