Zandra

No. Damage buff do not stack.

However, if you drink a +1 dmg buff, then a +2 damage buff. The stronger buff takes effect, and does not stack.

If you're trying to stack the alchemist's buff with the alchemist's buff, then yes, the stronger of the two buffs will take effect. You can however stack the alchemist's damage buff with the fisherman or cook's damage buff, since they're the only two consumables that stack across professions.