Adobe has updated their Reader mobile app for Windows Phone devices with new features. With this app, you can view wide variety of PDF types, including password-protected documents. The new features in the version are support for Acrobat.com and the ability to add comments by highlighting text and more.
Store and access documents in the cloud with Acrobat.com:
• Share files with anyone using Acrobat.com file sharing
• Share files across all of your desktop and mobile devices with Acrobat.com
• Automatically save changes back to the cloud
• Synchronize where you are reading across multiple devices via Acrobat.com
Download it here from Windows Phone Store for free.