When working with groups of objects many times you would like the objects appearing in scene scattered over the ground here and there or starting at random positions, this is done very easily wiht Pulldownit by setting initial states for rigid bodies. This is the procedure:

Lets say you start with a grid of objects you have created by cloning a single one using the duplicate tool of your 3D Platform.

Now you have to select all of them and create a dynamic rigid body for each object and then open the Dynamics properties window and set an initial velocity of (4,4,4) also set random values of (200,200,200), make the same for the initial angular velocities if you want random orientations aswell.

Now set your time range to about 10 frames  and play the simulation, you can also disable gravity if you prefer.

Ok, perfect, at the last frame all the objects has modified  quite a few  its initial position and orientation, now we have just to set this configuration as the initial state for the rigid bodies, for doing this, you have to bake keys for the simulation if you havent done it yet and after that click on Delete All Pdi bodies in the Manage Pdi World Window.

Now select all objects and move the slider to the last frame of the simulation, follow by deleting all keys for the objects, and you are done.

From here you can start a new simulation to drop the objects and scatter them over the ground, for this just set a dynamic rigid body for each object as before, open Pdi Simulation Options and enable Use Grid as Ground , make sure gravity is enabled this time, now set the extend of the simulation to 200 frames or so and launch it.

Nice, at frame 200 you get your objects stacked in a natural way, now you can set this configuration again as the intitial state of rigid bodies as we did before.