1. Google drive – This is a must. Upload your document to your google drive document and make it public for everyone. Google docs rank fairly well in search engines.
2. Upload the file on your own server (where your site is hosted) and make the link indexable by linking it from your site and/or blog. This way, that file will be part of your site and the search engine traffic will come to your site.
3. Upload your file on file sharing websites using sites like http://www.mirrorcreator.com/, http://multiupload.biz/ or http://embedupload.com/ which upload the files on multiple sites. Do note that most of the good sites do need login/password so you are better of creating them.
4. Upload your file on Docstoc.com and Scribd.com – I have seen content on docstoc and Scribd rank pretty well in search engines so you should upload your pdf ebook to them.
5. Upload your file on other web based file sharing – docstoc and scribd are not the only 2 sites where you can upload your files. Here are few more document hosting sites.
- https://www.dropbox.com/ (make sure to keep the file url public)
- http://www.free-ebooks.net/ (thre is a minimum 50 page limit, do check other terms too)