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 (including Mac OS X), 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, TrueType, or standard X fonts.

Xpdf should work on pretty much any system which runs X11 and has Unix-like (POSIX) libraries. You'll need ANSI C++ and C compilers to compile it. If you compile it for a system not listed on the xpdf web page, please let me know. If you can't get it to compile on your system, I'll try to help.

Xpdf is licensed under the GNU General Public License (GPL), version 2. In my opinion, the GPL is a convoluted, confusing, ambiguous mess. But it's also pervasive, and I'm sick of arguing. And even if it is confusing, the basic idea is good.

In order to cut down on the confusion a little bit, here are some informal clarifications:

• I don't mind if you redistribute xpdf in source and/or binary form, as long as you include all of the documentation: README, man pages (or help files), and COPYING. (Note that the README file contains a pointer to a web page with the source code.)
• Selling a CD-ROM that contains xpdf is fine with me, as long as it includes the documentation. I wouldn't mind receiving a sample copy, but it's not necessary.
• If you make useful changes to xpdf, please make the source code available -- post it on a web site, email it to me, whatever.

If you're interested in commercial licensing, please see the Glyph & Cog web site.