This is needed when okular view mode is set to facing pages. If a PDF file contains the PageDirection R2L, okular should default to display it in a right to left reading direction without a need to enable the option from the settings. Acrobat reader already does that.
Please attach such a file
Created attachment 112796 [details] PDF with PageDirection R2L
> strings rtl.pdf |grep -i direction /PageDirection /R2L