Yes. All traits with a "+" sign always stack. So, if you have Charge +2, and gain Charge +3, then you have Charge +5. This is the way most traits work.
Traits with a static number on them (with no "+" sign) do NOT stack. Currently, there are 2: AEGIS and REGENERATE. For the protection of the game system we could not allow these 2 traits to stack! If a creature acquires multiple traits like these, you only use the highest one.