I was CEO and co-founder of doxIQ (https://www.crunchbase.com/organization/doxiq), a similar product. We were acquired by Nitro, another PDF software company, after a couple of years. DocSend started around the same time as us and has become the standard for final format document tracking.

My suggestions:

- read analytics are valuable, but it's hard to get people to pay for that alone given how many other products offer it for free

- pick your target user persona (SMB vs enterprise) and focus on making them happy

- focus on integrations with other systems that your target persona uses, like CRM/marketing automation/email/etc

- ignore shiny object syndrome. you'll be tempted to add more analytics tools or insights to "add more value." while YMMV, i've found this to be a waste of time.