Ok, I'm just looking for a little clarification on the way damage is calculated here.

If I have a bow that does 1D8 and I have the feat PBS it bacially makes the weapon a 2D8. That sounds simple enough, but I was wondering if it Doubles the weapon damage, or simply adds an additioal die of damage based on what the original die number is. The reason I ask, is that if you add multiple sources of +1[W] to the equation, how do the numbers add up?

If the base weapon is 1D8, PBS makes it 2D8, does then each additional +1[W] just add 1D8 to the damage?

or....

If the base weapon is 1D8, and PBS makes it 2D8, if the +1[W] is a multiplier of the damage, would the next +1[W] make it a 4D8 weapon?

I know that much of the damage in the game is based off of Die rolls, so trying to determine the damage numbers are difficult as a 1D8 weapon can do 1 to 8 damage, but what im trying to figure out is how to explain the very high crit numbers that I see comming off of weapons that are affected by more than one +1[W] modifiers.

Thanks in advance, please use small words to help explain this, the morphine i take gives me a serious -INT penalty.