They don't. If you submit a PDF, the scribd system takes a copy and the link to their copy is inserted automatically.<p>I will never put a link to a PDF again. I submitted a link to someone's work, and scribd has effectively appropriated the traffic for themselves. It smacks of theft.<p>I contacted scribd to say that the author had not authorised them to take a copy and asking that they remove it, but they are aggressive in their defence of their actions. They require legal statements from the owners, and even then I'm not convinced.<p>Only submit a PDF if you're happy to have it copied without permission.
When you link to a PDF I think the site puts the [scribd] in - which links to a scribd'd version of the PDF.<p>(it took me a while to figure this out :) stumped me for an age when I first noticed)
scribd doesn't have pdf. it has documents in flash. i don't use flash (only flash video outside a browser). [scribd] makes me not click the link. seeing [pdf] might make me click the link. the sooner people stop using scribd for things i find interesting, the happier i am.