Probably the nearest you can do sensibly without getting to complex is provide a link to the PDF and make sure it has the correct MIME. For example:
<a href="example.pdf" type="application/pdf" title="Link to Example PDF document">[PDF document]</a>
Then obviously provide a link as to where you can download the PDF Reader. The browser will then be armed with enough information to search for an appropriate plugin if it doesn't already have such a reader.