I've seen people advocated of publishing PDFs to document sharing sites for the SEO purpose, but this was mainly from sales letters of people selling a software or similar service that publish your PDF to such sites. These days I have looked into these doc-publishing sites (box.com, docshare.com, etc.) and all of them convert your PDF into a flash presentation. Since search engines cannot crawl the flash I do not see the benefit from SEO perspective, because they cannot detect your backlink even though it exists in the document. Am I missing something or the PDF publishing is useless for the link building?