One of the main features of this app is the Skydrive sync, where you can connect your Skydrive account and access and read the files on your phone. PDF Reader is a free app to easily read a wide variety of PDF, XPS and CBZ files on your Windows Phone 8 device. PDF Reader is a relatively new app for reading PDF files on your Windows Phone 8.
Adobe had released a PDF reader for Windows Phone 7, but it is not yet compatible with WP8. While there is a default PDF reader app for Windows Phone 8 from Microsoft, it is always nice to have third party apps which might bring in additional features.