2009-06-12.

[not directly useable as of Ghostscript 9.05]

An irritating pdf file, containing modifiable fields, could only 
be opened in Adobe reader (not kpdf, xpdf, evince), and on 
printing to a postscript file, the postscript couldn't be turned
to sensible read-only pdf by ghostscript's ps2pdf command:

_____________________________________________________________
ps2pdf14  -sPAPERSIZE=a4   "R_.ps" "R_.pdf"
This PostScript file was created from an encrypted PDF file.
Redistilling encrypted PDF is not permitted.
Error: /undefined in --eexec--
-------------------------------------------------------------

Tedious of ghostscript to bother implementing the PDF standard 
properly!  The following fix, from 
http://www.linuxforums.org/forum/misc/51331-encrypted-pdf-files.html
worked fine (once the /right/ instance of the /pdfwrite was found
-- search for the string ".where"):

In the file:
	/usr/share/ghostscript/*/lib/gs_pdfwr.ps
find the line that lets later processing know that PDF is the 
final destination: in my ghostscript-gpl-8.62 this is line 734,
_____________________________________________________________
% Patch 'where' so that the distiller operators are only visible
% if the pdfwrite device is the current one.
{ currentdevice .devicename dup /pdfwrite eq exch /ps2write eq or{
    .where
-------------------------------------------------------------

replace "/pdfwrite" with something else, e.g. "/pdfwritenot".
Presumably it might be useful, with other more sensible input, 
to allow the destination to be known for optimisation reasons.
But for converting acroread's output postscript into a simple 
compatible-visible-but-not-modifiable PDF, it worked fine.