The user should include an link to http://www.adobe.com/products/acrobat/readstep.html  somewhere on the page to allow users to download the free acrobat  reader if the do not have it already.

Not much else has to be done from a Users point of view. Simply click the link to the PDF File. The setup will determine whether the file will be opened in the browser window (inline) or in an external adobe acrobat viewer window (works on Internet explorer, not on Netscape. Netscape will always open the PDF inline).