The rules are vague on this. However the only difference between a free action and a swift action is that it consumes more energy so you can only take one, but it consumes the same amount of time.
Core Rulebook; Combat wrote:
Swift Actions
A swift action consumes a very small amount of time, but represents a larger expenditure of effort than a free action. You can perform one swift action per turn without affecting your ability to perform other actions. In that regard, a swift action is like a free action. You can, however, perform only one single swift action per turn, regardless of what other actions you take. You can take a swift action anytime you would normally be allowed to take a free action. Swift actions usually involve spellcasting, activating a feat, or the activation of magic items.
And given that you can take a swift action whenever you can take a free action, I would say yes.
Core Rulebook; Combat wrote:
The Surprise Round:
If some but not all of the combatants are aware of their opponents, a surprise round happens before regular rounds begin. In initiative order (highest to lowest), combatants who started the battle aware of their opponents each take a standard or move action during the surprise round. You can also take free actions during the surprise round. If no one or everyone is surprised, no surprise round occurs.
