Portable Document Format (PDF) is a file extension. According to my opinion number of webmaster are looking for PDF sharing sites over the internet because that sites offer do-follow link as a referral site. I will recommend you to use in your off page techniques. You can generate high quality link form PDF sharing. Write an article with photo and save doc file in PDF format after then you can easily submit PDF file as an article.
I have share PDF sites with various SEO parameter such as Page rank, alexa rank, Moz rank, DA, PA, IP address and traffic. You can get website according to yourself requirement or according page rank. All the PDF sites are offering do-follow link for website. You should use this method to create high quality link with white hat techniques.
Top 100 PDF sharing sites List