|Lost In Limbo|
The rules don't specify. That said, I find that supplying at least enough information to get across whether you're getting through damage resistance is necessary to avoid breaking immersion. Pathfinder may use the Critical Existence Failure paradigm, but roleplaying it that way is quite silly. I don't give fractions, only what I would consider to be things a character would believably observe. When fighting a human, you could tell whether the human is bleeding from a dozen wounds and holding their intestines in with one hand. When fighting a stone golem or an ooze, however, it's far more difficult to tell how far gone the creature is.
|Bob Bob Bob|
I don't think there's specific rules for knowing your own attack/damage rolls but it's something that seems reasonable for characters to know. In real life it's relatively easy to tell if you did really well or really poorly, in theory our characters would be capable of much the same judgement.
As for damage reduction, "A creature with this special quality ignores damage from most weapons and natural attacks. Wounds heal immediately, or the weapon bounces off harmlessly (in either case, the opponent knows the attack was ineffective)." So you do know if an attack was ineffective against damage reduction.
I would never tell numbers, but part of proficiency is knowing how much damage an attack with X power behind it would deal. This means that they would know when thier attack isn't doing full damage. They could then verbalized it and allow others to make knowledge checks or retry them.
Usually, a successful Knowledge check let's you determine things like DR, and Energy Resistance.
I would think that a successful Heal check would help you better identify the damaged state of a creature, and you should be able to put the two together to have a good idea on how effective your blows are.
So the DR rules themselves say that when your hit doesn't penetrate it, you notice. Knowledge can warn you ahead of time, and clue you in on how to get through.
As for the other matter: knowing how much % of the monster's HP you just dealt? No rules that I know of, weirdly enough. I tend to give ballpark answers though, like "that didn't really impress him at all" or "that really hurt" or "that almost finished him".