The official DocuSign .NET library integrates electronic signature into applications and websites. It's available through NuGet, a central package repository for Microsoft development. This project contains pre-requisites, which consist on a DocuSign developer account to obtain a key and a quick start guide, that explains how to add the DocuSign .NET client, how to authenticate with DocuSign, and how to create a DocuSign envelope. The link, Examples.cs, provide code samples for this project.
So, you're trying to share some files with someone who only has access to an old version of Word. Or maybe that Microsoft-hating friend of yours who only uses WordPerfect. Perhaps you want that old-school ebook to be an epub, rather than .lit. For any of these problems, there are desktop apps that work, of course. However, sometimes you want to be able to do that within a program. If so, Doxument and the beautiful Doxument API are what you need.
Google has updated the APIs for Google Sheets and Google Slides, giving developers access to advanced tools such as image recognition, speech recognition, location and maps, and email and calendaring. Together with the Classroom API, enterprise developers have far more control over business apps.