Recently attempting to edit an Adobe PDF file, I read up on the format 
and opened it into emacs (23.0.60.1 GTK+ as packaged in Ubuntu 
"emacs-snapshot.")  I expected to see the textual content: %PDF-1.6 .....
Instead, WOW! emacs actually rendered the document.

The mode-line says "DocView" mode, and I can switch back and forth 
between rendition and text.  I haven't yet found whether I can modify it 
and correctly render the changes.  Before I can do that, I will need to 
decode the content streams contained in the original.  Obviously (I 
think) the code is in there somewhere in order for emacs to render the 
thing.

Then, I tried finding something about this "DocView" in the Info 
system.  Sorry, no cigar.  Then I tried googling my way through gnu.org 
for something about DocView.  No joy there either.  Without some clue as 
to what I'm looking for, it is not likely I'll find it.  And, without 
some Info help, it is not likely I can get full use out of it.

So, please, where do I find the code libraries and the documentation for 
this capability?

TIA
-- 
David A. Cobb, retired mainframe t-rex.