Get code for API access without prompting allow access

Hi,

I am building C# MVC web site which going to create document at the end and need to sign from end user. When I am start accessing Adobe APIs it required code retrieve first before retrieving access toke (refer: https://www.adobe.io/apis/documentcloud/sign/docs/#!adobedocs/adobe-sign/master/gstarted/get_access_token.md). Article mentioned it requesting allow access page and user should be sign in to adobe to get codes. Our end users does not have adobe account and we should generate that code with our adobe user id which authenticate through the API. When I am searching for such function seems it is not possible at the moment, is there way to do that? 

Thanks