They are done by the Shareholders Meeting. Proposals made by directors and corporations need a written report justifying the proposal. The SHM is called and the resoltion is or isnt passed.
A notarial deed is required at the Trade Registry. Publicity must be made to: Change corporate name, transfer address or change corporate purpose. Amendments implying new obligations for shareholders require their consent.
Capital increase: New shares or increased par value via a SHM resolution. Shareholders have preemtive rights to purchase new shares.
Capital reduction: Aims to reestablish balance between assets and equity by writing off, reducing par value, or grouping shares.