When viewing the "Player Board" display, you have the option to organize players by "Rank" or "Name" order.
You can change this by selecting the "Sort by..." drop-down menu.
If you are holding an in-person draft, and don't want owners in attendance to see players by rank, then you can sort them "By Name" (alphabetical).
There is no option to hide the player rankings from owners who are drafting remotely. Just there is no way to prevent a remote owner from viewing several outside sources for player rankings, there's no way to hide FanDraft's ranking order.l