Open any Arabic text file ( one is attached ). Okular shows an empty page. Reproducible: Always
Created attachment 94771 [details] an arabic txtfile
KEncodingProber doesn't work correctly with this file. This causes Okular to not be able to read this file. A similar bug can be found here: https://bugs.kde.org/show_bug.cgi?id=334733
Confirmed on Okular from git master, it shows a blank file.
*** This bug has been marked as a duplicate of bug 334733 ***