Paul Porter, Esq. was a senior partner at Pearson Specter Litt, who specialized in bankruptcy.
Back when the firm was known as Pearson Hardman, he was shown to be loyal towards Daniel Hardman, a loyalty Daniel claimed existed even before Pearson Hardman was founded. In order to secure his vote Jessica Pearson had Harvey help him on one of his bankruptcy cases, in which Paul was attempting to have his client file for bankruptcy. Harvey however managed to get his client the loans he desired from the bank. Angry that Harvey had refused to do what he asked, he lost Jessica's vote and instead voted for Daniel. When Daniel usurped Jessica as managing partner, Paul got Harvey Specter's office on the 50th floor (which used to be Jessica's office) and Harvey got his on the 46th floor.
Following Hardman's dismissal, Harvey got his office back and it is presumed Paul got his old office on the 46th floor.