PdfStandardStructureTypes.TableOfContents Field
A list made up of table of contents item entries (TableOfContentsItem) and/or other nested table of contents entries (TableOfContents).
A TableOfContents entry that includes only TableOfContentsItem entries represents a flat hierarchy. A TableOfContents entry that includes other nested TableOfContents entries (and possibly TableOfContentsItem entries) represents a more complex hierarchy. Ideally, the hierarchy of a top level TableOfContents entry reflects the structure of the main body of the document.
Supported in PDF/UA-1.