The Pay is low across the board, they make a song and dance every year about performing salary equity analysis in comparison to other PR firms around the same size but it's total BS. You will be paid less than your peers regardless of the team or position you hold.
Additionally, the tech they utilize is awful. You're going to get set up on a hand me down that's a blink away from fully dying. Even the brand new right out of the box devices sometimes have major issues. C-Suite and Finance would rather save budget on VP bonuses than invest in agency wide new laptops. It's all very short sighted, they would rather incrementally purchase new devices and give them out to more senior staff with device issues and to new senior hires, those on older devices will have to wait until theirs fully dies before they even think about setting you up on a new one.
Finally, unless you're on one of the PR teams don't even think about upwards mobility. Every other team from HR to Finance to even parts of Digital will eventually hit a ceiling in promotions. Not like the promotions matter much anyway, you'll get a nominal increase but your day-to-day responsibilities stay the same but know you have additional work to do as well! So you end up still feeling junior.