All perfect praise be to Allaah, The Lord of the Worlds. I testify that there is none worthy of worship except Allaah, and that Muhammad, sallallaahu ‘alayhi wa sallam, is His slave and Messenger.
We have already issued Fatwa: 82753 clarifying that there is no confirmed Sunnah prayer before the Friday prayer, so please refer to that.
However, it is permissible for a person to perform whatever number of supererogatory prayers he wants before the Imaam steps on the pulpit, as the Prophet, sallallaahu ‘alayhi wa sallam , said: "Whoever performs a ritual bath (Ghusl) and then comes to the Friday prayer and prays whatever [number of Rak’ahs] it is predestined for him to pray, and then listens to the Imaam until the end of his sermon, the sins committed between that Friday and the previous Friday – as well as that of three more days, will be forgiven.” [Muslim]
The saying of the Prophet, sallallaahu ‘alayhi wa sallam: "And prays whatever [number of Raka's] it is predestined for him to pray," is evidence that it is permissible to perform supererogatory prayers before the Friday prayer.
Allaah Knows best.