How does atmospheric pressure vary with altitude?

Atmospheric pressure decreases with an increase in altitude. The gravitational force at the surface(lower altitudes) is higher. Therefore, the force between the earth and air molecules is higher at lower altitudes. So because of much higher gravity, the molecules are present more at the surface and decrease as the altitude is increased.

We know that the more the molecules, the more pressure they apply.

Thus the atmospheric pressure is more at lower altitudes and decreases as the altitude increases.