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, TrueType, or standard X fonts.

There are four additional utilities (which are fully described in their man pages):
1. pdfinfo -- dumps a PDF file's Info dictionary (plus some other useful information)
2. pdffonts -- lists the fonts used in a PDF file along with various information for each font
3. pdfdetach -- lists or extracts embedded files (attachments) from a PDF file
4. pdftoppm -- converts a PDF file to a series of PPM/PGM/PBM-format bitmaps
5. pdfimages -- extracts the images from a PDF file

The license of this software is Free, you can free download and free use this pdf software.