You can use sniping for hitting flat-footed from range, without using feint.
If you’ve already successfully used Stealth at least 10 feet from your target, you can make one ranged attack and then immediately use Stealth again. You take a –20 penalty on your Stealth check to maintain your obscured location.
This penalty to maintaining the stealth can be reduced by taking Expert Sniper, and eventually you can snipe twice in a turn using Master Sniper.
Alternatively, if you can make an enemy shaken as a free or swift action somehow, you could use Shatter Defenses, to make them flat-footed to you.
Any shaken, frightened, or panicked opponent hit by you this round is flat-footed to your attacks until the end of your next turn. This includes any additional attacks you make this round.