Comment 24 for bug 270046

Confirmed. This is an old bug from at least Intrepid, possibly Hardy. It's still present on Jaunty:

Mon Apr 27 21:07:41 2009 [DEBUG] switching to new gid (lpadmin)
Mon Apr 27 21:07:41 2009 [DEBUG] initialization finished (v2.5.0)
Mon Apr 27 21:07:41 2009 [DEBUG] user identified (ward)
Mon Apr 27 21:07:41 2009 [DEBUG] output directory name generated (/home/ward/PDF)
Mon Apr 27 21:07:41 2009 [DEBUG] user information prepared
Mon Apr 27 21:07:41 2009 [DEBUG] spoolfile name created (/var/spool/cups-pdf/SPOOL/cups2pdf-27444)
Mon Apr 27 21:07:41 2009 [DEBUG] source stream ready
Mon Apr 27 21:07:41 2009 [DEBUG] destination stream ready (/var/spool/cups-pdf/SPOOL/cups2pdf-27444)
Mon Apr 27 21:07:41 2009 [DEBUG] owner set for spoolfile (/var/spool/cups-pdf/SPOOL/cups2pdf-27444)
Mon Apr 27 21:07:42 2009 [DEBUG] found beginning of postscript code (%!PS-Adobe-3.0)
Mon Apr 27 21:07:42 2009 [DEBUG] now extracting postscript code
Mon Apr 27 21:07:42 2009 [DEBUG] found title in ps code (([ubuntu] [SOLVED] apparmor cupspdf in Hardy [Archive] - Ubuntu Forums))
Mon Apr 27 21:07:42 2009 [DEBUG] found end of postscript code (%%EOF)
Mon Apr 27 21:07:42 2009 [DEBUG] all data written to spoolfile (/var/spool/cups-pdf/SPOOL/cups2pdf-27444)
Mon Apr 27 21:07:42 2009 [DEBUG] trying to use PS title (([ubuntu] [SOLVED] apparmor cupspdf in Hardy [Archive] - Ubuntu Forums))
Mon Apr 27 21:07:42 2009 [DEBUG] removing trailing newlines from title (([ubuntu] [SOLVED] apparmor cupspdf in Hardy [Archive] - Ubuntu Forums))
Mon Apr 27 21:07:42 2009 [DEBUG] removing enclosing parentheses () from full title (([ubuntu] [SOLVED] apparmor cupspdf in Hardy [Archive] - Ubuntu Forums))
Mon Apr 27 21:07:42 2009 [DEBUG] removing special characters from title ([ubuntu] [SOLVED] apparmor cupspdf in Hardy [Archive] - Ubuntu Forums)
Mon Apr 27 21:07:42 2009 [DEBUG] truncating title (_ubuntu___SOLVED__apparmor_cupspdf_in_Hardy__Archive__-_Ubuntu_F)
Mon Apr 27 21:07:42 2009 [DEBUG] title successfully retrieved (job_637-_ubuntu___SOLVED__apparmor_cupspdf_in_Hardy__Archive__-_Ubuntu_F)
Mon Apr 27 21:07:42 2009 [DEBUG] input data read from stdin
Mon Apr 27 21:07:42 2009 [DEBUG] output filename created (/home/ward/PDF/job_637-_ubuntu___SOLVED__apparmor_cupspdf_in_Hardy__Archive__-_Ubuntu_F.pdf)
Mon Apr 27 21:07:42 2009 [DEBUG] ghostscript commandline built (/usr/bin/gs -q -dCompatibilityLevel=1.4 -dNOPAUSE -dBATCH -dSAFER -sDEVICE=pdfwrite -sOutputFile="/home/ward/PDF/job_637-_ubuntu___SOLVED__apparmor_cupspdf_in_Hardy__Archive__-_Ubuntu_F.pdf" -dAutoRotatePages=/PageByPage -dAutoFilterColorImages=false -dColorImageFilter=/FlateEncode -dPDFSETTINGS=/prepress -c .setpdfwrite -f /var/spool/cups-pdf/SPOOL/cups2pdf-27444)
Mon Apr 27 21:07:42 2009 [DEBUG] output file unlinked (/home/ward/PDF/job_637-_ubuntu___SOLVED__apparmor_cupspdf_in_Hardy__Archive__-_Ubuntu_F.pdf)
Mon Apr 27 21:07:42 2009 [DEBUG] TMPDIR set for GhostScript (/var/tmp)
Mon Apr 27 21:07:42 2009 [DEBUG] entering child process
Mon Apr 27 21:07:42 2009 [DEBUG] GID set for current user
Mon Apr 27 21:07:42 2009 [DEBUG] UID set for current user (ward)
Mon Apr 27 21:07:42 2009 [DEBUG] ghostscript has finished (256)
Mon Apr 27 21:07:42 2009 [DEBUG] no postprocessing
Mon Apr 27 21:07:42 2009 [DEBUG] waiting for child to exit
Mon Apr 27 21:07:42 2009 [DEBUG] spoolfile unlinked (/var/spool/cups-pdf/SPOOL/cups2pdf-27444)
Mon Apr 27 21:07:42 2009 [DEBUG] all memory has been freed

Note that ghostscript error code.

The only option I've found so far is disabling apparmor entirely for cupsd.