How to do an indexed replace?

Questions
1

Hello!

Is it possible to do repeated replace for “k” according to its position in a list like this?

list = {Subscript[a, k], Subscript[a, k] + Subscript[b, k], Subscript[
  c, k], Subscript[d, k] + k}

Jesus

2

I have found this in the documentation.

n = 1; {x, x, a, b, x, x, c, d} /. x :> n++

Just what I need!

Thanks