D&D had a table of target DCs, with Easy, Moderate and Hard difficulties over a range of levels. Is there an equivalent somewhere for Pathfinder?
You mena 4e? In general, a more Pathfinder/3e approach is to not scale DC with level. If you don't know the DC of something, the answer is probably 'about 15'.
I use the following sort of guidelines:
DC 5: Things that kids struggle with but adults usually do pretty well - bake a cake, for example.
DC 10: Things that are hard to do. You'd normally hire a professional to attempt this sort of thing.
DC 15: Things that require a fair amount of skill to do reliably.
DC 21-24: Things that only heroes can usually do. Olypic quality performance if you hit this regularly. You are one of the best in the world if you don't do this by luck. If an action movie hero can do it, it really should be in this DC.
DC 25-30: Things that only superheroes can do reliably. This level of DC means you are doing something really impressive and astounding. Normal humans can aspire to hit this sort of achievement on their best days.
DC 40: Things that only a demigod can do. Note that I think that the Epic handbook typically made epic uses of skills too hard. DC 40 is roughly what I consider the difficulty of running across a pool of water by balancing on it, or running up a wall without even grabbing it with your hands, leaping into a 3rd story window, or pulling down a castle with your bare hands. Characters that can make these sort of checks should appear to be magical.
Being able to take 20 on a task sort of messes this up a little. If it is something people normally take a lot of time on, add 10 to the DC's above.