Firma translates to "signature", a word that isn't common in romantic songs. This makes its use here especially powerful and memorable.
In "Un Papel", Prince Royce sings about a relationship that is reduced to "un anillo y una firma en un papel" (a ring and a signature on a paper). This imagery evokes the cold, formal finality of a divorce, a poignant end to a love story that began years ago.
Have you ever looked back on a relationship and wondered how it all fell apart? That's exactly where Prince Royce is in "Un Papel". He starts by thinking about how fast time flies and how it can leave you with some emotional scars, singing, "Cómo pasan los años, los años, los años nos dejaron heridas" (How the years pass, the years, the years left us wounds). He remembers a specific day, a first of March, when he was just a boy and she was beautiful. He'd give anything to go back to that moment, to dance with her and have a drink together one more time.
But here's the twist. Despite all this nostalgia, they are now "dos extraños" (two strangers), drifting further apart. The only thing left from their time together is a legal document, what he calls "un anillo y una firma en un papel" (a ring and a signature on a piece of paper). It seems like they got married, but the marriage itself is gone, leaving only the paperwork behind. And just when you think it's all romantic sadness, he throws in a final, funny line about her: "No cocinaba tampoco limpiaba" (She didn't cook or clean either). It's a little dose of reality after all the daydreaming.