"se las ingeniaba"

[Rusty]

What you're seeing here is «ingeniárselas para», which is a verbal locution. The reflexive pronoun 'se' will change to match the subject (Pascal). Both the reflexive pronoun and the 'las' (static - it never changes) precede the conjugated verb.
The resulting phrase can be translated as 'managed to' («encontró un modo de»).
So, «era la manera en la que Pascal se las ingeniaba para conseguir que le sirvieran en las tabernas» means "was the way Pascal managed to get himself served in the taverns."