pdf editors

[Patrick Wagstrom]

Sorry if this message breaks the threading, but I receive the messages
in a digest mode, so it's hard for me to reply to a particular message.

The compressed nature of PDF files really isn't the problem, they're
just compressed using zip compression[1], nothing big.  If it was the
problem, then it would be impossible to read the file.  (As an aside,
Acrobat 6 introduced additional compression mechanisms I'm not familiar
with.)

The issue is that these file formats; PDF, PS, EPS, etc; are made not to
be edited.  They're designed so I can put out a piece of work and ensure
that it stays the same on everyones computer.  They're a little like
flash in the sense that both files originate from some other underlying
format and must be transformed into the distributable format (ie
latex->pdf, of the flash movie->swf).

Creation of PDF files obviously isn't much of a problem as there are a
variety of packages that can easily do this.  What is the bigger issue
is that most of the libraries for manipulating PDF files weren't
designed with editing in mind.  Furthermore, the document doesn't store
enough information to make it easily editable.  There is no concept of
"word wrap" inside of a PDF document.  While it is possible to edit a
document using the full version of Acrobat, you're still limited by what
you can do.  For example, changing text frequently breaks spacing.

Also, one of the issues with PS files is that they're a series of
instructions that tell the renderer/printer how to move around.  Usually
positions are given relative to the previous.  Removing stuff or
resizing it would require recalculating of items, not difficult, but not
a pressing reason to do it.

If you want to experiment, most PS files are nothing more than text
files, you can go in an try hacking these on your own.  Adobe is even
nice enough to put a free reference manual online[2], but it's over 900
pages, so have a good time.  They also have the complete PDF reference
manuals available too [3] at a mere 1100+ pages.

--Patrick


[1] http://www.prepressure.com/pdf/info/compression.htm
[2] http://partners.adobe.com/asn/developer/PDFS/TN/PLRM.pdf
[3] http://partners.adobe.com/public/developer/pdf/index_reference.html