Another forum was debating this - but hoping for a Paizo clarification/errata....
lets do an example: monster AC 26 your to hit is a +4 and you roll a natural 20..
Page 278: When you make an attack and roll a natural 20 (the number on the die is 20), or if the result of your attack exceeds the target’s AC by 10, you achieve a critical success (also known as a critical hit).
To me it seems like on an attack roll a 20, you hit and its a crit per page 278
but page 445 seems to contradicts this saying you need to exceed by 10.... its a normal hit, but not a crit.
|Taja the Barbarian|
...If you rolled a 20 on the die (a “natural 20”), your result is one degree of success better than it would be by numbers alone. If you roll a 1 on the d20 (a “natural 1”), your result is one degree worse. This means that a natural 20 usually results in a critical success and natural 1 usually results in a critical failure. However, if you were going up against a very high DC, you might get only a success with a natural 20, or even a failure if 20 plus your total modifier is 10 or more below the DC. Likewise, if your modifier for a statistic is so high that adding it to a 1 from your d20 roll exceeds the DC by 10 or more, you can succeed even if you roll a natural 1! If a feat, magic item, spell, or other effect does not list a critical success or critical failure, treat is as an ordinary success or failure instead.