As of version 5.0 of PDFKit.NET you can create and consume tagged PDF documents.
What is tagged PDF?
A tagged PDF has additional information that is referred to as the logical structure of the PDF. The logical structure is a hierarchy of structure elements that exists separately from the visual content. The logical structure is associated with the visual content by bi-directional pointers. A piece of visual content is said to by tagged if such a pointer exists and the corresponding structure element is referred to as the tag.
The following Adobe Acrobat screenshot shows a piece of text being tagged as a paragraph:
Purpose of tagging
Tagged PDF allows the following types of applications: