Do you offer any pay-as-you-go or API request based pricing?
At our lower tiers, no, but if you're looking at doing a significant amount of requests happy to talk about bulk pricing - ed [at] hellosign [dot] com
Do you have a NodeJS SDK?
Tom, not currently but it's on our roadmap. If you shoot me an e-mail at ed [at] hellosign [dot] com, happy to notify you as soon as it's ready.
Dev at HS, here. For our launch we prioritized the top SDKs our community requested. Those SDKs were Java, Ruby, PHP and Python. We know there are a lot of requests for a NodeJS SDK and are looking into how it will fit into a future release. We don't have an official date, but additional sdks (and node.js, in particular) are on the top of our minds.