how can i print with original size

I print a pdf file in web,like this

<object id="pdfObj" classid="clsid:CA8A9780-280D-11CF-A24D-444553540000" width="0" height="0" border="0">

<param name="src" value="test.pdf" />

</object>

pdfObj.PrintAll();

when I print it with PrintAll, it's indistinct

but I print it with dialog,set original size，print ok

pdfObj.PrintWithDialog();

now，how can i set this parameter in code？

help！thank you！