Plotting a mark in gr()

Dear all,
I have the simple code in to plot two set of points:

using Plots 
gr(size = (1500, 1000),fmt=:png,ylims=(0,100), xlims=(0,100))
as = rand(1:100,100,2)
scatter(as[1:50,1], as[1:50,2],mc=:blue,ms=8,msw=0,markershape = :square,labels="Fornecedor primários")
scatter!(as[51:100,1], as[51:100,2],mc=:red,ms=8,msw=0,markershape = :square,labels="Fornecedor secundário")

At right of each point, I would like to print the number of each point (a small label). How can I do this?

Check out the docs for annotate