Ghostscript
Welcome to Ghostscript, an interpreter for the PostScript language and for PDF.
The leading edge of Ghostscript development is under GPL license, as is the latest release, Ghostscript 9.05.
Ghostscript can be downloaded here, and from sourceforge.net.
We keep online documentation for the development tree and many previous releases in the documentation archive.
We have also started collating a Frequently Asked Questions page. It is early days, but may prove useful:
Other page description languages:
A user-friendly viewer: