"He was able to read."
Translation:Il a pu lire.
The passé composé ai pu / as pu / a pu ... etc would be very commonly used. The word pouvoir being used here is the verb meaning "to be able". There is also a noun pouvoir which means "power", for example au pouvoir = "ïn power". Remember, verbs have past participles and can be conjugated, nouns cannot.