When an airplane goes supersonic, it creates a shock wave in front of it. The shock wave compresses the air and slows it down so the speed component orthogonal to the shock front becomes subsonic. See it this way: The airplane sort of creates it's own cocoon of denser and less voluminous air to fly in.
As in subsonic flow, the highest pressure is found behind the tip of the shock wave, in a stagnation point, a point where the speed is reduced to zero, like on the leading edge. The lowest pressure and density is usually found before the shock wave, this is the normal atmospheric pressure. Differently to subsonic flow, in supersonic flow every change in flow speed comes with a large change in density.
There are 2 types of shock waves:
- the normal shock wave:
They have nice tables where you can see the speed, pressure and density behind the wave. This shock wave mostly occurs in pipes, like a pitot intake.
- Oblique shock waves:
These shock waves are called strong when the mach number after the wave is below 1, and weak when the speed after the wave is still supersonic.
NASA has some nice programs to show how different types of shock waves are formed and how they interact, you can find them here.
The highest pressure is found at the stagnation point of a part which directly faces the oncoming flow. This is the stagnation pressure and it rises with the square of the flow's Mach number. Since a supersonic wing is usually swept, its leading edge will not reach the full stagnation pressure because the flow's speed component orthogonal to the leading edge is not changed.
The lowest pressure is normally found on the upper side of the fuselage. Air is so rarefied there that the vertical tail surface becomes increasingly ineffective at higher Mach numbers. The inclination of the local surface away from the direction of movement can be used with the Prandtl-Meyer expansion calculation to give you a rough idea how low this pressure can drop.