Gets or sets the annotation rectangle in default user space, normalized; setting it keeps the appearance, which §12.5.5 then maps onto the new rectangle; [0 0 0 0] when Rect is missing or malformed.
public PdfRectangle Rect { get; set; }
ISO 32000-2 §12.5.2, Table 166 (required), and §7.9.5: any two diagonally opposite corners, so an unnormalized rectangle is legal.