The app is free to download and use.
From the Scribd Blog:
With Scribd for iPhone, our valued users can access their content, collections, reading feed, and community while on the go. Everyone can also access a plethora of content on the app, including an array of editorial publications curated by Scribd editors everyday. With the app it’s easy to explore, read, and share millions of written works across the Scribd ecosystem.
The app allows users to access features that are popular with Scribd’s engaged user base, such as the Reading Feed, documents and collections while they’re away from their desktops.
Enjoy your favorite Scribd content fully optimized for the iPhone. The app’s PDF Reader makes for an ideal experience for reading documents.
The PDF reader can also come in very handy for reading documents outside of Scribd. When you browse the mobile web and stumble upon a PDF file, select to send to Scribd and you will automatically be placed in the Scribd iPhone app PDF Reader for an optimal reading experience.
Learn More/Download via iTunes App Store