This is fantastic - I just sent a prospect a proposal to execute. I had thought about EchoSign but I just didn't want to deal with what looked to be an enterprise-y solution. I just emailed HelloSign support asking if it was possible to copy and paste a link to a document that needs signing so that I can paste that link into my Basecamp messages to my prospects. For now I prepare my Basecamp message and prepare the document for signature and ensure I post the BC message a few seconds ahead of sending the proposal via HelloSign.