I'm not sure exactly what you are trying to accomplish, however...
If you just link the pdf to something (either a text link or an image) the pdf will open in the browser (if the user has the plugin) or will prompt the user to save the file. If the pdf does open in the browser, the user can save the file from there.
I hope this helps, but I get the feeling you just want the user to be able to click a link and the pdf will automatically download to their desktop. I'm not sure how to do that.
Best of luck,
las7098