Create a simple link:
<a href="myfile.pdf">Click here to open</a>
Many browsers will probably open the PDF file in the same window, so if you want users to actually download it, you might have to add a note saying "right-click this link and choose Save Target As..." Alternatively, ZIP the pdf files, then it'll probably give you a download dialog box.
<a href="myfile.zip">Download a zipped pdf</a>
I think enough people are familiar with downloading PDFs to make the first option the safest. After all, why force people to download and unzip?