This lists more generic documentation about certain Platform SDK end-points and resources:
And this lists resource URLs to perform operations and links to various request/response structures for XML and JSON:
For more in-depth support, I am guessing DocuWare will tell you that you need to purchase specific Platform SDK support. That's what I was told when I asked about using the Platform Services from a non-.NET environment (we use Visual Foxpro). On that front, here are a couple links to forum posts about all that (including authentication):
The XMLHTTP object built into Windows internet API stack (we switched to that from ServerXMLHTTP) is just a wrapper on HTTP requests and responses that you should be able to mimic in node.js. All of my code is in Visual Foxpro, which probably looks ugly to the non-Foxpro eye, but it is fairly straightforward to get the gist of it.