So there's no UI, yet, for changing keybinds, but there is an ini file + commands way of doing things.
The commands are ExportKeybinds and ImportKeybinds.
ExportKeybinds takes an optional path. If you don't supply one, your keybinds will go into the Keybinds folder in your installed PFO (e.g. C:\Program Files (x86)\Pathfinder Online\Pathfinder_Data\Keybinds). If you do supply a path ("ExportKeybinds C:/go/here/please/arglebargle.ini"), then it'll put your keybinds there.
Let's assume you just typed "/ExportKeybinds", cuz calling your keybinds arglebargle is weird.
You now have a file called "player_settings.ini". It is in your Pathfinder Online\Pathfinder_Data\Keybinds directory with 2 other files: default.player_settings.ini and default-dvorak.player_settings.ini.
Open up your player_settings.ini lovingly with you most prized text editor.
Gaze in wonder at your keybinds.
You may now edit your keybinds. Notice how they have been laid out in a format thusly:
key = command
I have tried to be very understanding in what is an acceptable name for a key. Generally just typing the key works. If you want to use the keypad keys, you have to say so. "1" is the key above Q and Tab. "alpha1" is that same key. "keypad1" is way over on the far side of the keyboard.
So, if you wanted ESDF for movement instead of WASD, you would take this:
w = forward
s = back
a = turnleft
d = turnright
q = strafeleft
e = straferight
And turn it into this:
e = forward
d = back
s = turnleft
f = turnright
w = strafeleft
r = straferight
And then, when you have finished editing your keybinds, save your file and thank your beloved text editor for the fine job it did.
Journey forthwith back to PFO, and type this into your chat input:
(Note: If you were weird and put your keybinds somewhere else, you can "/ImportKeybinds C:/somewhere/else/player_settings.ini". However, I have a command args processing bug that doesn't take kindly to spaces in your file path, currently. >.>)