用DevMode字段可以！
如设置纸的Width:
procedure TPrintForm.SetWidth(PaperWidth: longint);
var
ADevice, ADriver, APort: String;
ADeviceMode: THandle;
DevMode: PDeviceMode;
begin
SetLength(ADevice, 255);
SetLength(ADriver, 255);
SetLength(APort, 255);
{ If ADeviceMode is zero, a printer driver is not loaded. Therefore,
setting PrinterIndex forces the driver to load. }
if ADeviceMode = 0 then
begin
Printer.PrinterIndex := Printer.PrinterIndex;
Printer.GetPrinter(PChar(ADevice), PChar(ADriver), PChar(APort), ADeviceMode);
end;
if ADeviceMode <> 0 then
begin
DevMode := GlobalLock(ADeviceMode);
try
DevMode^.dmFields := DevMode^.dmFields or DM_PAPERWIDTH;
//or DM_PAPERWIDTH;
DevMode^.dmPaperLength := PaperLength;
DevMode^.dmPaperWidth := PaperWidth;
///////////////////////设置纸张////////////////
finally
GlobalUnlock(ADeviceMode);
end;
end
else
raise Exception.Create('Could not set printer copies');
end;
