I have a pdf generator which generates a pdf and directs to data url, is it possible for me to take the pdf from dataurl and add as document ?
It's not possible to simply specify the URL where a file resides, and have DocuSign automatically read that file and add it to an Envelope. Instead, your application will need to read the file and then write the byte stream to the "Create Envelope" API call request body, when calling DocuSign to create the envelope.
As Kim mentions, you can not specify the document through a URL, however if you write the document bytes to a local file, then make the Request Signature on Document API call and supply that file in the request, you would be able to create a DocuSign envelope with the PDF(s) inside it.
Have you seen the DocuSign API Walkthroughs? There's sample Node.js code (and 5 other languages) that you can plug in your credentials and run- this gist in particular is for the Request Signature (Create Envelope) API call:
https://gist.github.com/Ergin008/5505764
And you can find the all the other sample code gists here:
https://www.docusign.com/developer-center/quick-start/api-explorer