Saint Paulinus was born at the city of Premariacco in north eastern Italy around 725 AD during the end of the Lombard rule. He attended the patriarchal school at Cividale before becoming an Ordained priest and serving as the master of the school and learning Latin. This education in Latin culture and language would prove invaluable to Saint Paulinus the rest of his life. When the King of the Franks (Charlemagne) conquered Lombard Italy in 774 AD , Charlemagne rewarded Saint Paulinus's loyalty with the property of Waldand.
The same year Saint Paulinus was invited to the court of Charlemagne to serve as the master of grammar. When the Patriarch of Aquileia, Patriarch Sigauld died in 787, Saint Paulinus was consecrated as the new Patriarch of Aquileia. He immediately set out implementing new reforms and taking an extremely active role in leading the community. In 792 AD, he took part in the Council of Ratisbon (the condemning of the heresy of Spanish Adpotionism - that taught Jesus was the adoptied son of God) and in 794 AD at the Frankish council at Frankfort which again condemned Spanish Adoptionism.
Saint Paulinus travelled with Pepin (Charlemagne's son) in 796 AD in military campaigns against the Avars and presided over a synod of Bishops on the banks of the Danube after the Avars' defeat to determine programs of evangelization and catechesis for the Avars and Slavs. The synod was also responsible for assigning the patriarchate of Aquileia's northern territory to the Bishop of Salzburg (with the consent of Saint Paulinus), an agreement that lasted from 811 AD (when it was confirmed by Emperor Charlemagne) almost a millennium. The Slovenes regard Saint Paulinus as their apostle who brought the religion of Christianity to them in peace. Saint Paulinus would then preside over the Council of Cividale where he opposed Adoptionism again, expounded on the Catholic doctrine of the Holy Trinity, and affirmed the double procession of the Holy Spirit from the Father and the Son (filioque).
Though he often conflicted with Charlemagne, Saint Paulinus served as one of his missi dominici (envoy's of the Lord) at Pistoia with several other bishops and traveled to Rome in 798 AD as a legate to Pope Leo III. Saint Paulinus wrote several works of poetry including the Cramen de regula fidei, a Versus de Lazaro and an elegy inspired by the death of his friend, the Duke Eric of Friuli. He also composed 8 different liturgical hymns to be sung at Christmas, Candlemas, Lent, Easter and the feats of Saint Mark, Saint Peter, and Saint Paul.
Saint Paulinus died on January 11 in 802 AD in the town of Cividale. After several translations of his relics, Saint Paulinus' relics were laid to rest under the altar of the cry of the basilica of Cividale del Fruili.