Adobe has released a PDF reader for iOS that is compatible with password locked PDF's and supports files secured by the company's Adobe LiveCycle Rights Management, a DRM scheme that is Adobe offers to enterprise clients. Our sister site AppShopper has more on Adobe Reader:

Adobe is a little late to the game with an app for the digital document standard it created in the early 90?s since dedicated PDF-viewing apps, like GoodReader, ReaddleDocs and others, have been available in the App Store for some time. However, it appears to be the only PDF-viewer currently in the App Store that supports files secured by Adobe LiveCycle Rights Management, a DRM protection scheme that’s part of a suite of enterprise-level products and services offered by the software company.

Adobe has a number of apps available on the App Store, including Photoshop companion apps Eazel, Nav, and Lava on the iPad, and Photoshop Elements 9 Editor on the Mac App Store.

Adobe Reader is a free download for iPhone and iPad from the App Store. [Direct link]