Which is the best method for correcting water the pH level ?

Which is the best method for correcting water the pH level ?

Dear All, We produce drinking bottle water in 5US gallon poly carbonate bottles and distribute to consumers. Our reverse osmosis water has pH level of 5.4 -5.5, would it be right to add the caustic solution to enhance pH of water to 6.9-7.4 ? Can we use any other chemical/material without having any health problems? Please suggest some methods for correcting our water pH level.