This class represents the thread dictionary. This is definitively detailed in:.

The ISO PDF Specification, ISO 32000-1:2008 PDF 1.7; Table: 160, page 376.

The ISO PDF Specification, ISO 32000-2:2017 PDF 2.0; Table: 162, page 457.

This class is always an indirect object because BeadElement.EntryT, CatalogElement.EntryThreads and ThreadActionElement.EntryD require it to be so.

System.Object
    WebSupergoo.ABCpdf14.Elements.Element
       WebSupergoo.ABCpdf14.Elements.ThreadElement

A thread dictionary is the root of an article thread. A thread groups a sequence of bead regions across one or more pages so that a viewer can present them as a continuous reading flow.

The F entry is the first bead in the thread's circular linked list. Following N (next) references from that bead and back to the first visits every passage in reading order.

The I entry is an optional information dictionary carrying descriptive metadata such as title, author, and subject.