There appears to have been some controversy and it looks like you have to pay to download most stuff from Scribd now.
Scribd - Wikipedia, the free encyclopedia
The last paragraph under Controversy -
[In August 2010, Scribd began beta testing premium services including the Scribd Archive. The test was met with minor community backlash leading Scribd to make changes to its policies[clarification needed
]. Now when trying to download almost any document from Scribd, users are asked to pay for it first via their premium content service.]