I'm on FreeBSD and have compiled and installed the graphics/okular port (i.e. not much else of KDE4 other than okular's dependencies.) This has installed version 1.8.0. I start my X11 manually with startx and use FVWM as the window manager.
When I open a PDF with okular and click a link to, say, https://en.wikipedia.org/wiki/ISO_8601, a dialog box opens saying
Select the program you want to use to open the file ISO_8601
I select /usr/local/bin/firefox. Then okular downloads the file ISO_8601 to a local directory, $HOME/.cache/kioexec/krun/13965_0/ISO_8601 and opens that file with firefox. The result is ugly, since all the CSS style is missing.
How can I make okular not download an URL, but pass it straight to firefox? I'm willing to hack mailcaps, mime-types, or even frob KDE XML files deep down in my directory tree.
The file is available here. See page 4, link to ISO. The PDF is created with DocBook and Apache FOP 2.3 as the final conversion step to PDF.
Other readers, such as qpdfview do open the link directly in Firefox.