So, Admiral Akbar has the following

"During an engagement, play this unit from your hand as a participating unit on your side'

My question is can I play this after the edge battle in the action phase or do I have to bring him out before the edge battle?

Wheelz said:

Actually, the answer is "yes" to both situations.  Ackbar comes out in any Action window if you're using that ability.  The key part you didn't highlight when quoting his text is the Action: part.  That's really what decides when it can work.  So look at the charts on pages 30-31 and anywhere you see a dark blue box labeled "Player Actions" is where you can use Ackbar's ability to deploy him, both on your turn and your opponent's.  In an engagement, here's when you can play Ackbar;

After the active player declares attackers, but before the opponent declares defenders

After opponent declares defenders, but before the edge battle

After the edge battle is completely resolved, but before the player who won the edge battle makes their first strike

Any moment between strikes thereafter

Agreed.

You have to be smart when to play him with the opponent having any Tactics out that might effect him in the turn of things. It would suck to play him and then he gets focused……

Since the active player always gets first action in an action window, you could, if you won an edge battle, take your first strike then play ackbar immediately afterward. 

Another question about this, does Ackbar come down for free, or does he come in in the middle of an engagement for his cost of 3?

Page 13, Term Summary, Play. 

btw A cool combo i have been using…

play Ackbar

use his text

cover fire him

and when able replay him and use his text again :)

cleared a few battles like that

though it does cost 6 resources.

Combo I used off this effect:

1. Engage objective with Leia

2. Opponent blocks with 2 characters, 1DC and 2DC… I win edge.

3. Strike with Leia, dealing damage to 2DC character.

4. He strikes Leia, killing her, thus he captures her, removing all focus tokens.

5. Play Ackbar, killing both opposing characters, and focus out his remaining units so they can't attack next turn.

6. Sit back and smile.