The download option is shown to logged out users too, so you should see it. But you do have to be registered in order to compete the download. With regard to y

The download option is shown to logged out users too, so you should see it. But you do have to be registered in order to compete the download. With regard to your other point, we think that the conversion of the PDF to HTML 5 and a couple of other things we do on Academia.edu massively increases the visibility of your paper as compared to hosting it on a department webpage. This is a huge benefit for the individual researcher in increasing the impact of their work and the number of people who find and use it.