This is a simple plugin which allows someone to edit signs.
It works off a system where each player has a "selected sign", which they can then use a command to edit.
/se or /signedit to edit the sign[line] means line number (1 to 4) and [data] means text to type in.Note that should your input message be too long for the sign, it will be cut off at the nearest space or when no more characters can fit.