With a normal airline? You walk up to the gate, say you lost your paperwork (boarding pass, ticket, doesn't matter), show your ID, and get a new boarding pass issued within about a minute of managing to get someone's attention. At least that was my experience. No hassle, no fee.

Ryanair? I would expect them to offer you their boarding pass printing service for only $99.99 (you missed the $49.99 special that was only available until 4 hours before boarding, silly you).