Why does Obama use different pens when signing a bill?

It is not just Obama. Many presidents have switch pens for every document signed. These pens are then given as gifts to dignitaries, museums, originator of the documents and other associated reasons.

So he can give them away as gifts and souvenirs.

I cant really gove you an answer,but what I can give you is a way to a solution, that is you have to find the anglde that you relate to or peaks your interest. A good paper is one that people get drawn into because it reaches them ln some way.As for me WW11 to me, I think of the holocaust and the effect it had on the survivors, their families and those who stood by and did nothing until it was too late.