Issuu is a professional online PDF sharing service website, or it can also be considered as a pretty good online PDF document library. Issuu is another website I really like after Scribd, and I think Issuu should have a good development prospect. Through Issuu, you can upload and share your own PDF documents, use it as an online PDF document storage website, or share PDF documents on your website or Blog via the services provided by Issuu. Moreover, Issuu classifies different PDF documents to facilitate readers' browsing.