Portable Document Format (PDF) is a file format
developed by Adobe Systems for representing documents in a manner
that is independent of the original application software, hardware,
and operating system used to create those documents. A PDF file can
describe documents containing any combination of text, graphics,
and images in a device independent and resolution independent
format. These documents can be one page or thousands of pages, very
simple or extremely complex with a rich use of fonts, graphics,
color, and images. PDF is an open standard, and anyone may write
applications that can read or write PDFs royalty-free.
In addition to encapsulating text and graphics, PDF files are most
appropriate for encoding the exact look of a document in a
device-independent way. In contrast, markup languages such as HTML
defer many display decisions to a rendering device such as a
browser, and will not look the same on different computers.
Free readers for many platforms are available: the free Adobe
Reader by Adobe Systems, the free Foxit Reader [1], and several
free open source readers, including Xpdf for POSIX-like systems
with the X Window System; KPDF, a viewer based on Xpdf for KDE;
GPdf, a derivative of Xpdf for GNOME; Evince, a document viewer for
GNOME (fork of GPdf) that can view PDF-files; GSPdf and ViewPDF
[2], for GNUstep; and front-ends for many platforms to
Ghostscript.
Proper subsets of PDF, collectively called PDF/X, have been
standardized by ISO.
for more info, pls refer to wiki
or
www.adobe.com
