If you are looking for a fast, reliable, trouble-free, lightweight PDF viewer, and you stumble upon xPDF in your distro's app listings -- keep stumbling. Chances are it will not run on your Linux configuration. In theory, xPDF is a promising alternative to PDF viewers available for the Linux desktop such as Adobe PDF Viewer, Okular and Evince. It is a fast and light application that does not exhibit sluggish performance.