0.Pathfinder is built on D&D 3.5. And while not all the verbiage carried over, the rule structure is still built on the same foundation.
DMG 3.5, page 26: "Don't allow players to use the ready action outside of combat."
Logical spam. All the members of party "A" ready an action and move down a corridor. All the members of party "B" ready an action and move down the corridor...
If the game really had wanted all players to add 4 to their AC (total defense) prior to combat starting, there are easier ways to state that.
The very concept of standard, swift, move actions are defined under Combat, in the CRB, pages 162&ff. The things a character might do are adjudicated into a type of action based on things like time and effort.
Pathfinder is a rule system that you must find a rule that permits you to take an action. Without that rule, all actions are prohibited.
IN combat, you are allowed to ready actions; you are allowed to fight defensively or take the total defense action.
Outside of combat, there are no rules. It is therefore not permitted.
Getting back to the question at hand.
You cannot fight defensively out of combat; you cannot take total defense out of combat.
You cannot take actions out of combat; action types are solely defined in combat, aka what happens after initiative is roll
Initiative and the surprise round are designed to handle that transition from out of combat to combat. Attempting to cheese Total Defense is minimizing the value of dex; the importance of perception etc.
High dex character (such as rogues, monks) usually go first. Are they really so overpowering that they need the additional malus of always striking characters that are total defense? Really?
Addressing Hey I Can Chan's question vis-a-vis wizards casting spells with std action casting times out of combat.
Outside of combat, action doesn't occur in combat rounds. The ref adjudicates how things happen sometimes on a round by round basis. The fact that it is useful to use standard actions as a construct outside of combat doesn't alter that under the rules actions are defined only in combat.
More to the point, how long does an attack action take? A swift action? These things are purposely left vague; they do not have a hard value. Rather the are all regarding the actions you can take in combat. As mentioned previously, a combination of time and effort.
And it isn't that these arbitrary things exist, just simply that by the rules you aren't allowed to take them.
The rules exist in pathfinder for transitioning from out of combat to in combat.
Both sides aware: You roll initiative. Whoever goes first gets the privilege of taking their actions first.
Allowing people to take actions outside of this is breaking the rules that exist on surprise etc.