WinRtPdfViewer (nuget): A PDF Viewer Control for Windows Runtime Platform [WinRT] for Windows 8.1 Universal Applications (Mainly a Solution for Windows Phone 8.1 Issue Missing PDF Reader).  It can be used for both Windows 8.1 & Windows Phone 8.1 for a unified UX/UI.  It is built over PDF.js developed by Mozilla.
Keywords: Adobe|PDF|Reader|Viewer|WinRT|Windows8.1|WindowsPhone8.1|Universal|Windows|Runtime