function SetPdfPrintMode(PrintMode: TPdfPrintMode): Boolean;
Selects the print backend used by FPDF_RenderPage when feeding the platform printer.
Windows 上默认值为 prEmf;在 PostScript 设备上使用 prPostScript* 可避免重复光栅化。
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在调用页面作用域操作之前;需要打开文档的方法会引发EPdfError otherwise.SaveAs to persist.
begin
TPdf.SetPdfPrintMode;
end;