Many businesses like to produce content in PDF format. Ideally, you’d take the time to convert this content into HTML and SEO the text afterwards. However, that’s not always possible and the PDF’s must be deployed onto a website. Fortunately search engines are capable of indexing PDF content as long as it’s text and not graphically based.
From the staff at Search Engine Land comes a great post with Eleven Tips For Optimizing PDFs For Search Engines. We highly recommend you give it a read and apply these tips.