The practice of PDF submission is currently booming in the world of online marketing. It is a good source for backlinks. Your article or PDF submission will be manually submitted to the best document sharing websites. You will receive dofollow backlinks from this service, and your file will remain up indefinitely.
I'll mention some well-known sharing websites, like Scribd, SlideShare, Issue, 4Share, and Zoho.
Key Features of this service: