After poking around bugs.kde.org I have found this bug:
https://bugs.kde.org/show_bug.cgi?id=205088
And the link in this comment:
http://www.pietzowski.de/pdf/ (optional append index.php)
User: user
Pass: pass
Reproduces the PDF problem in Konqueror.
If anyone else is using konqueror I would be interested if they also get the
same problem.