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 and the X Window System.

Xpdf is designed to be small and efficient.  It does not use the Motif
or Xt libraries.  It uses standard X fonts.  Xpdf is quite usable on a
486-66 PC running FreeBSD.

WWW: http://www.foolabs.com/xpdf/