I’ve just published a book (very narrow field of interest). I don’t want to spend time/money on converting it to ebook because it shall appeal to v small audience. Could I lodge a pdf on Dropbox and then send a link to as many users that express an interest? I’m not concerned about getting payment but I want to be sure that this would work. If so what is the best (economical) plan for one file > unspecified number of downloaders.