Created attachment 106409 [details] one can see that a unique tab take all the width When several files are open in one okular instance and one of the files has a name substantially longer than the rest (here more than 3 time) it will take all the window width making unreadable the others tabs.
Can you try the patch at https://git.reviewboard.kde.org/r/128062/ ? I think it is meant to solve your problem.
(In reply to Oliver Sander from comment #1) > Can you try the patch at > > https://git.reviewboard.kde.org/r/128062/ ? > > I think it is meant to solve your problem. I have not the slightest idea how to try that patch. But if he does what he advertise I believe it would be a great addition to Okular.
*** This bug has been marked as a duplicate of bug 363513 ***