how about a request form that ostensibly takes an email address and a name, and an optional text field and then automates the process of sending the paper (or a hidden (unique) link to that paper) to that email address. it need not store those details anywhere, except that it optionally sends an email to the author (if there is a message). the only concern is spam.
Or better... have an email address like papers@authorname.com which receives requests with the title of the paper in the subject line, and a piece of software then receives the request, waits for a random amount of time (anywhere between 10 mins to a couple hours), and then sends the paper to the requester.
It would seem that the author personally received the email and replied with an attachment as a "professional courtesy", while completely automating the process in the background.
that would be to hard to use. the idea is to make the experience as similar as possible to clicking a link to download without making the document directly available for download, but make it look like a personal request that could be handled manually. by submitting a form, that is achieved. the form ensures that the right document is selected, and the process can be automated without error. but for all we know, it just sends an email to the author who might handle the request personally.
