What would this latin sentence mean : "Prout necessitas ferat atque experientia suffragetur" ? No idea... Note: found in this link
There is an official English translation at the link you provided (labelled "EN" at the top right-hand side), which gives "as need arises and in the light of experience" as the official Vatican translation of this phrase.
Translated overly literally, it means "according as necessity carries and experience counsels".