Some clients can’t understand the value of HTML- and still want pretty pictures of their PDFs. This little tutorial is the ticket if you want to actually display a PDF in your post:

These are the steps to embed PDF files into a page or post for clients, enabling a visitor to read the PDF document right from the page. The process of embedding PDF files into a WordPress post is fairly simple, assuming your using a WordPress version later than 2.6.- click the following link to see the full instructions

via Embed PDF in WordPress.

You can also make a stock icon- like the Adobe Acrobat document icon, store it in your media library- and then link to the image, which should allow faster page views.