This actually needs a litle more context, Sonia.

Outorgar usually means grant or bestow,as mentioned above, and in that case would be done by the seller who alone has the power to do this.

The Aurelio gives as he Juridical meaning of "ourtogar":

5. Jur. Declarar em escritura pública.

and I believe that this is what it means in this sense.

So I have included in my translation the "Public" aspect which is stated in he original, since this very likely takes place at a public registry office which it would not in the UK or US.