Gets or sets the font of the text, a font of the document being signed; null (the default) uses Helvetica,
which shows WinAnsiEncoding text only. Use an embedded font for other text and for PDF/A.
public PdfCanvasFont? Font { get; set; }
ISO 32000-2 §9.6.2.2 (Standard 14 fonts) and §9.7 (embedded composite fonts).