Comment 6 for bug 1023840

Most Runners/Desktop-Shortcuts/... use .desktop files to start an application. If the system-wide (== default) .desktop says "--unique" the user is faced with a unique-application. If there is an open "unique"-window, e.g. pressing the launch-button only will acitvate that window. Activating windows is IMHO the job of the window manager.

Unique applications definitely make sense. A Music player, for example. Video player is another thing: You can watch a film and simultaniously watch sports (without sound). E.g. vlc offers an option to allow only one window.
Viewing documents (e.g. pdf) is not bound to one document at a time. I often have several documents open and watch them side by side. It also happens, that I view one single file in more then one window (e.g. the C++ Standard - having several paragraphs open at a time is useful, otherwise you would need to scroll around/work with bookmarks (which will reset if scrolled)/...)

But that is MY WAY to work. I can't say if the majority of the users needs to view more then one document at the same time (or one document more then once). I can live with the default and simply place a .desktop-file in my $HOME. I just hope that qpdfview won't change the executable name, the icon path, MimeType/Categories/... :D