In the Fedora 27 version of okular the multiple page view mode of pdfs shows pages in reverse order (lowest page number on the right).
Can you attach a screenshot? Are you sure you didn't enable RTL mode on the settings?
If you can provide the information requested in comment #1, please add it.
Sorry about the confusion, figured out that there is a (new?) setting in Program Features -> "Right to left reading direction" that was selected by default when I upgraded from FC26 to FC27.