Thank you for your tip, but for any reason It din't work.
If I understood correctly I had to create the file koreader/settings/event_map.lua
containing the assignations to the keys...
I've been playing with this, that was what I understood:
Return { [1] = "LPgFwd", [272] = "LPgBack", }
I tried too
Return { [1] = "LPgFwd", [272] = "LPgBack", }
And any combination of them, but did't work
Thankyou anyway