Create an insertable "stamp"

This is probably very simple however, I have not been able to figure it out
yet. I sometime need to e-mail a document where I would like to add a kind of
"stamp" if you will. Like the yellow"sign here" sticker thing you see on real
documents. I have seen it before in Adobe but not sure how to get it in my
tool bar. I would like to be able to create my own stamp to say "new" or "new
info", and I would like to be able to insert it and to resize it . Any
ideas??