Best way of Inserting a PDF/link into a DW page?

Link to the PDF as if it were another web page.

If the user has Acrobat, it will show in their browser or in Acrobat, whichever they have set as their default viewer.

Or, if you want to ensure it downloads to the user's machine, you can zip the file, then link to it as you would another page. It will download to their machine and require un-zipping before viewing.