The Jurisdiction of the Notary

A notary is a public official authorized to draw up deeds both between living persons (i.e. sales, exchanges, divisions of property, loans etc) and last will and testaments, witness them publicly, keep and issue copies, certificates (i.e. summaries) and extracts (i.e. partial copies) (article 1 of the notarial law). 
A deed drawn up by a notary is a public document, because the notary is authorized to bear witness to it (hence he is a public official) and as such carries particular legal force: statements made in a notarial deed (e.g. that the document has been read to the parties, or that a person has made or signed a declaration in his presence) provides full evidence (in other words must be considered as true, even by a judge), unless falsification has been proved.  
The law calls for notarial deeds for those events and contracts for which it is necessary to guarantee the maximum degree of legality in terms of identity of the parties and conformity to their wishes, because such acts are considered significant: for their social and economic content or complexity (e.g. sales, divisions of property, loans and other real-estate contracts, deeds of constitution of commercial companies and modifications to social status, constitution of associations for the purpose of becoming juridical entities, etc); for the effects they may have upon the civil status of a person (e.g. recognition of a natural child); and for the public interest in the expression of a person's will and its accurate rendering in legal language (e.g. wills, donations).