The author of the plugin has the instructions on the ‘Description’ tab of the plugin page. I don’t think there is a shortcode ‘button’, if that’s what you’re looking for, but he does list the actual shortcodes to use.
I have a PDF uploaded to my site, and I use the shortcode:
[scribd-url url=”http://mydomain.com/uploads/pdf/my-file.pdf” pubid=”123456789″]
When you are on a page or post go to the “text” view (as opposed to the “visual” view) and paste that shortcode into it.
Replace the URL with your own (wherever you’ve uploaded your file that you want to display), and replace the PUBID with the publisher ID that you get when you sign up for a Scribd API account. My publisher id looked like this: pub-123456789, but I used just the numbers for the shortcode above. you can sign up here: http://www.scribd.com/developers
There is also an option to embed a document that you’ve uploaded to the Scribd site, as well as other options for the shortcodes, like width and height – check the description page to see more.
Hope this helps!
I just updated the plugin to provide a shortcode button in the editor. That should make it a bit easier to embed a document and access the various options in the shortcodes.
Note that you’ll need to be using WordPress 3.9 or above to get access to the new shortcode button.