function CreateDocument;
Closes the current document (if any) and starts a brand-new empty PDF.
The new document has zero pages until AddPage / ImportPages is called.
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.CreateDocument;