Var
DeviceHandle : THandle;
ADevice,ADriver,Aport : Array[0..255] of Char;
DevMode : PDevMode;
begin
DeviceHandle := Printer.Handle;
Printer.GetPrinter(ADevice,ADriver,APort,DeviceHandle);
DevMode := GlobalLock(DeviceHandle);
DevMode^.dmDuplex := DMDUP_HORIZONTAL;
GlobalUnlock(DeviceHandle);
end;
DMDUP_HORIZONTAL:用水平页面旋转格式双面打印。