The style of an annotation's border, the S entry of a border style dictionary.
public enum PdfBorderStyle
ISO 32000-2 §12.5.4, Table 168. A name the table does not list reads as Solid ("a PDF processor shall tolerate other border styles"), without a diagnostic.
kind:method, kind:property, kind:ctor. Press Esc to clear.BeveledB: a simulated embossed rectangle that appears raised above the page.DashedD: a dashed rectangle, with the dash pattern of DashPattern.InsetI: a simulated engraved rectangle that appears recessed into the page.SolidS: a solid rectangle surrounding the annotation (the default).UnderlineU: a single line along the bottom of the annotation rectangle.