Version: 1.9.6 (enterprise 0.20070907.709405) (using KDE 3.5.8, Kubuntu (gutsy) 4:3.5.8-0ubuntu3.1) Compiler: Target: i486-linux-gnu OS: Linux (i686) release 2.6.22-14-generic An attached pdf file is not opened by kpdf, although the software tries to open kpdf at first (shows in the system tray) but than vanishes again. When you choose to open with, for instance, Acroreader all works fine. And when saving the file to desktop and than opening it with kpdf works fine too.
Your KDE is probably misconfigured, PDFs work fine for me. See also bug 141077 (and the other reports mentioned in there) for this. Or this is either bug 143237. Closing this, please reopen if those two bug reports are ruled out.