There are no universal guidelines for setting the price of your work on Scribd. You can charge as much as you like for your content, though you must charge at least $1.00 USD. Remember that Scribd charges a 20% consignment fee against the price of the content.
The ideal price of a document depends on a number of factors, including but not limited to its length, its topic, how well-advertised it is on other sites, the quality of the writing and the research you put into the work. Because of this variability, Scribd cannot recommend the price at which you should set your document. When setting the price of your work, it may be helpful to ask yourself, "If the work were sold as a physical book in a book store, what would other people be willing to pay for it?"
You can set your content's prices either at upload time or on an item-by-item basis by editing document properties.