This resource is now archived (won't be updated to newer versions) as Minecraft 1.20 finally added this much-needed functionality once and for all!
Simple one class plugin to allow signs to be edited by right-clicking it (while main hand empty + offhand not holding any dye item). Only works if you have permission to place blocks at that location. (If BlockPlaceEvent is not cancelled)
There is a permission editablesigns.use that is true by default There is also a command /editablesigns reload with the permission editablesigns.reload which does what you think it does
(Tho not tested, should in theory work on 1.8 - 1.16 as well)
