How do I remove a /pex suffix

try using this
https://github.com/PEXPlugins/PermissionsEx/wiki/Commands

if you have any more issues please feel free to pm me
and i also have a pex help thread if you or anyone else has issue please post on it
and i will reply as soon as possible http://www.planetminecraft.com/blog/permissions-ex-troubleshooting/

i have PEX and have used it extensively on my server, after you get the hang of
the commands and the .yaml its a very useful plugin as it can be very complexly configuired. also give the PEXrank plugin a try it will shorten your promotion command to /rank {name} [rank]

I recommend using groupmanager. Much more easier to use.

just type the same code, but instead of typing a new suffix, just put "" (two double quotes)
like for prefix... /pex user bob prefix ""... Will reset bob's prefix...