Pros
I have learned a lot in my time at DocSend that has helped to shape my career development. If you're eager to be surrounded by super smart people, dive into a fast-paced environment and get involved with a lot of diverse projects cross-functionally, I'd recommend applying. There's collaboration top-down and everyone is super open to helping and teaching one another. The People Ops team is the best I have worked with in my career and they genuinely have your best interests at heart.
Cons
Stress levels are pretty high, as expected at a tech startup. So long as you ask the right questions during your interviews about the day-to-day responsibilities and set expectations for how you're looking to contribute, you shouldn't have problems. You have to be very upfront about your needs and wants, because management is moving very quickly and they rarely have time to stop and ask if your needs are being met from a long-term growth perspective.