I think it would be a good idea to have a preference in the user profile to disable the iPaper integration.
Personally, I don't mind getting PDFs or other documents, and I love the way Evince displays them on Ubuntu. However, I can see how many on Windows could prefer to have the iPaper integration on in order to not bother with Adobe Reader.
Now I can download the PDF only if I really want it on my hard disk (which is definitely the rare case). Otherwise the PDF's just like a well-typeset web page. Very slick.
Right now you can see the link to the original PDF just by right-clicking on the post title. But yeah there should be a link to the original PDF either in the post or in the document page. We are working on it :)
As someone else mentioned, this won't work with iPhone or any other browser without Flash installed, so I shouldn't have to view the iPaper-ized version just to get to the PDF.
I don't think scribd automatically publish it on the Internet beyond where you paste it (not certain of that). So I am not sure what it could change in your mind about getting permission.
Flash may work better than PDF on Windows, but this is definitely not the case on OS X, especially iPhone, which doesn't even have Flash but is great at displaying PDFs.
It would be nice if there were even just a small .pdf link right next to the bigger URL. Or a way to disable iPaper integration completely.
Personally, I don't mind getting PDFs or other documents, and I love the way Evince displays them on Ubuntu. However, I can see how many on Windows could prefer to have the iPaper integration on in order to not bother with Adobe Reader.