Now when you think on a free service you have to have in mind some limitation:

• Limited space for your files
• Limited bandwidth for your files
• Slow downloads – not important for smaller files
• Ads on download page – could be unprofessional for company’s
• Files could be deleted if there are not downloaded for a while
  

PDF-Archive – limited to 20 MB / file, there is no account needed witch make upload fast but in this case you dont have a file manage system and you dont know if your file is deleted or not. You can make your file public or private. PDF-Archive have some useful tools like: Repair a PDF file and Protect a PDF file (using a strong 128-bit encryption and two access passwords)

FreePDFhosting – this service need you to have an account. On a free account your file is limited to 2 MB /  file and you can upload just 5 files. Files are hosted for 30 days no mater if you have downloads or not. If you make a donation (this is like a premium account) this things change

Google Docs – This is a document hosting service who can give you possibility to edit your file online, share files, let users download or print your files and there you can set public writes to a file and everyone can edit it. You have 1 GB for your files it is fast, no minim file size and unlimited bandwidth.

Scribd – this is not just a PDF hosting site is a document hosting site. Your files can be read for free from scribd site but can not be downloaded from free. There is an option to sell your documents in the Scribd Store. This make Scribd a great tool to sell your ebooks.

PDFFileShare – free account, PDF can be uploaded from you personal account. Download link send you to a page where you can preview your PDF or read it from that webpage and save it to your computer. Files are indexed and available for public do download or can be private. There is an option to embed your file in your website. There is no mention for a file limit or limited download speed/bandwidth (this dont mean that there is not any restrictions )

PDFHost.net – this is simple and basic. You have the option to upload file and receive your download link on your email.  There is no way to delete your file, no protection. There is no FAQ information like minim file size or how many day is keept . This is not recomanded for hosting your files maybe just for sending a file to a friend.

You will find there:

• Overall income-generation strategy
• Traffic, traffic, traffic
• How to build traffic
• Will putting ads on your site hurt your traffic?
• Multiple streams of income
• Blogging software and hardware
• Comments or no comments
• Build a complete web site, not just a blog
• Posting frequency and length
• Perks

Read more and … more on the article below
http://www.stevepavlina.com/blog/2006/05/how-to-make-money-from-your-blog/