Adobe Systems, which invented the PDF, this morning published its official PDF document reader for Windows Phone 8. Download it now
With the free Adobe Reader you can open and read a wide variety of PDF documents, including ones that come password protected. Built-in features include the ability to copy and paste, search the text for specific words, and zoom in on a page. Navigate docs quick with thumbnails, then read page-by-page or in continuous scroll mode. Hyperlinks and bookmarks are supported, too, so you can jump directly to a webpage or to a particular section of a PDF.
Give it a try and let me know what you think.