Sorry for so long without notice. On my box this problem occurs with _every_ pdf file. I have no problems with e.g. jpg files or so. As an example I attach one of the files for which I verified that it doesn't open upon double-clicking (giving the cited error message instead).
** Attachment added: "Example file for bug 19101" http://librarian.launchpad.net/5804269/0411112.pdf -- nautilus's clever anti-hax0r detection is really dumb https://launchpad.net/bugs/19101 -- desktop-bugs mailing list desktop-bugs@lists.ubuntu.com https://lists.ubuntu.com/mailman/listinfo/desktop-bugs