Xpdf is an open source viewer for Portable Document Format (PDF)
files. (These are also sometimes also called 'Acrobat' files, from
the name of Adobe's PDF software.) The Xpdf project also includes a
PDF text extractor, PDF-to-PostScript converter, and various other
utilities.

Xpdf runs under the X Window System on UNIX, VMS, and OS/2. The non-X
components (pdftops, pdftotext, etc.) also run on Win32 systems and
should run on pretty much any system with a decent C++ compiler.

Xpdf is designed to be small and efficient. It can use Type 1 or
TrueType fonts.

Xpdf is licensed under the GNU General Public License (GPL)