What a shell shows in a note or popup for an annotation: its text, author and subject, the popup's rectangle and state, and the replies to it. A model only; the shell draws it.
public AnnotationNote(PdfAnnotation Annotation, string? Contents, string? RichText, string? Title, string? Subject, string? Modified, PdfRectangle? PopupRectangle, bool IsOpen, IReadOnlyList<PdfMarkupAnnotation> Replies)
The annotation the note belongs to.
The text (Contents).
The rich text (RC) of a markup annotation, as stored.
The author (T) of a markup annotation.
The subject (Subj) of a markup annotation.
The modification date (M) as stored.
Where the popup shows (its Rect in default user space), or null without one.
Whether the popup is open initially (Open).
Markup annotations on the same page replying to this one (IRT without RT /Group), in page order.
ISO 32000-2 §12.5.6.2 (markup annotations, Table 172) and §12.5.6.14 (popup annotations); spec #33 viewer capability 6.