He made the text bigger, so we were able to read it.
(Place a comma before "so".)
could (modal auxiliary) — general ability, anytime, whenever (occurs in present, past and future contexts)
so (coordinator, connective, pronoun, adverb, discourse adverb, and more) – See "So" Uses.
vague (Adj) — unclear, can be understood in more than one way
was/were able (VP) — single occasion ability; managed to do something (past contexts)
"Text." by J. Sevastopoulos, 12 Oct. 2016. CC BY-NC-SA 4.0 International.