This will sometimes happen if you have modified the original pdf in Acrobat. If the pdf was rotated, even if the orientation was switched from portrait to landscape, the imported pdf will print upside down.
If you can, open the pdf with Acrobat, save it as another app (doc,xls) and create a new pdf with the desired layout...of course if you are pressed for time, do as Matthew suggested and rotate the imported drawing 180 degrees.