When I open okular without specifying a file, I am presented with:
That annoys me - and as a more serious concern, if I have been working on sensitive document titles, I don’t necessarily want them to be visible by default, as soon as I open okular. There doesn’t seem to be any command line options or settings that control this behaviour.
Is it possible to avoid showing recent documents?
The behavior you’re hoping for looks to fall somewhere under some existing items already open in KDE’s Bugzilla - in short, this looks to be a long-standing question of how to manage across KDE apps/components:
https://bugs.kde.org/show_bug.cgi?id=458103
https://bugs.kde.org/show_bug.cgi?id=464968
Well, not really - my question is more about displaying the list at startup; the list of recent documents as such is useful to me, and I do use the one in the menu; I just don’t want to see it at startup.
But, to comment on the bug reports you listed - I’m surprised that the length of the list is hardcoded at all, that seems unsophisticated, lets say. This kind of things are easy to set up, even in a GUI, and should be parametrized.
I see what you’re saying now - perhaps a workaround could be to change the .desktop file that opens Okular from the launcher to one that opens a blank / placeholder file, so that “welcome” screen isn’t seen? You could even make your own personal welcome screen to the program and use that as the pdf? 
