Antonio was born in Binondo, Manila in 1902. He was orphaned by the age of 12, and had to work in the daytime in order to finish his high school education at night. He studied architecture at the University of Santo Tomas but dropped out of school in order to assist in the design and construction of theLegislative Building (now, the National Museum of the Philippines).
Ramon Arevalo, the engineer in charge of the Legislative Building project, funded Antonio's education at the University of London. He completed a five-year architecture course in three years, graduating in 1927.
Antonio first came into prominence in 1933 with the construction of the Ideal Theater along Avenida Rizal inManila. His work caught the eye of the founder of the Far Eastern University in Manila, Nicanor Reyes, Sr., who was looking to build a school campus that was modern in style. Between 1938 to 1950, he designed several buildings on the university campus in the Art Deco style. The FEU campus is considered as the largest ensemble of surviving Art Deco architecture in Manila, and in 2005, it received an Honorable Mention citation from the UNESCO for the body's 2005 Asia-Pacific Heritage Awards for Culture Heritage Conservation.
Antonio also designed the White Cross Sanitarium (1938) along Santolan Road in San Juan City, and the Manila Polo Club (1950) in Makati City. He likewise designed the Ramon Roces Publications Building (now Guzman Institute of Electronics) in Soler Street in Manila, the Capitan Luis Gonzaga Building, and the Boulevard-Alhambra (now called Bel-Air) Apartments Building in Roxas Boulevard & where Manila Bay Hostel is located on the 4th floor, this Bel-Air Apartments is near T. M. Kalaw Avenue & beside Miramar Hotel. Bel-Air Apartments building was designed by Pablo Santonio and built in 1937. 
Apart from the Ideal Theater, Antonio also designed several other theaters in Manila, including the Life Theater, the Scala Theater,...