[flups]

I found a solution for Ubuntu 13.04.

1. Open /usr/bin/xdg-open as root
2. go to the sub routine open_lxde()
3. After the line
   
   local file="$(echo "$1" | sed 's%^file://%%')"
   
   add the following two lines:
   
   local printf=/usr/bin/printf
   file="$($printf "$(echo "$file" | sed -e 's@%\([a-f0-9A-F]\{2\}\)@\\x\1@g')")"

The problem is, that the lxde_open() is quite of buggy. This sub tries to convert an URI that starts with "file://" to an absolute path, but I fails to deal with special chars like %20. So

file:///home/lib/Isaac%20Asimov.pdf

becomes

/home/lib/Isaac%20Asimov.pdf

This is not a valid file name. So the known "file or directory not found"-window appears.

I c&p the above two lines from the "open_generic" subroutine where this is done right.

Thanks to Kovod for the hint with xdg-open.

"Guten Rutsch" from Germany and a happy new year!