function AddPage;
Creates a new blank page with the given dimensions in points.
Pass Index = -1 to append; otherwise insert at the given zero-based position. After AddPage the new page becomes current.
Wraps the corresponding PDFium API and exposes it as a TPdf instance member so consumers do not have to manage FPDF_DOCUMENT handles directly.
Pdf1.Active before calling page-scoped operations; methods that require an open document raise EPdfError otherwise.SaveToFile to persist.
if Pdf1.Active then
Pdf1.AddPage;