What is xpdf?
Xpdf is a viewer for Portable Document Format (PDF) files. (These are also sometimes also called 'Acrobat' files, from the name of Adobe's PDF software.) Xpdf runs under UNIX or VMS and the X Window System.
What is pdftops?
Pdftops converts Portable Document Format (PDF) files to PostScript so they can be printed.
For more information, see the manpages, or the author's page at http://www.contrib.andrew.cmu.edu/usr/dn0o/xpdf/xpdf.html