Translation of documents can be either certified – meaning they were completed by a professional translator or a translation that has been notarised.
In cases where a notarised translation is required, the translations can be done by anyone and does not require a translator or professional. However, the individual that completed the translation will be expected to declare the accuracy of the translation to the best of their knowledge and sign an affidavit stating exactly that.
It is recommended, especially if you are immigrating to a new country, that you have all of the translations done by a certified translator. This simply eliminates the risk of anything being declined or rejected for logistical reasons when it reaches its destination.