My character is invisible.
Does using either use of Intimate, to force to act friendly or demoralize, render my character visible?
Do they count as an attack? I don't believe they count as a spell.
The wording on Invisibility says that targets may speak freely.
Do those uses of intimidate break the spell?
Per the magic chapter of the Core Rulebook:
All offensive combat actions, even those that don't damage opponents, are considered attacks. Attempts to channel energy count as attacks if it would harm any creatures in the area. All spells that opponents resist with saving throws, that deal damage, or that otherwise harm or hamper subjects are attacks. Spells that summon monsters or other allies are not attacks because the spells themselves don't harm anyone.
Emphasis mine. Using Intimidate against an enemy is an offensive combat option, so it would break your invisibility.
I have no sources, neither have I much experience, but as it seems to not be welcomed to have partial answers in comments, here I go with an answer:
I suggest you rule this by situation. If the player tries to intimidate somebody by doing something that could show where he is, e.g. making a noise, roll for the target's perception with a fittingly hard or easy DC. I wouldn't rule in this case that the invisibility ends, but the enemies are temporarily aware of the approximated location if they roll high enough.
It seems like the 5e PHB would not even let them make a roll - but this is not the edition you asked for and I don't have the pathfinder one at hand.
An invisible creature is impossible to see without the aid of magic or a special sense. For the purpose of hiding, the creature is heavily obscured. The creature’s location can be detected by any noise it makes or any tracks it leaves. (PHB p. 291, Conditions)
