This C# WPF app program downloads and uploads a document from and to a SharePoint Online site.
Open the solution in Visual Studio and build it. Optionally, for your convenience, add the installation directory (the folder with the resulting executable) to your PATH environment variable.
You will need to register the custom "signdoc" protocol to be handled with this application.
In the project directory, in
etc/ you can find
customaction.xml which is the file that
defines the custom action button for list items inside your SharePoint site. To install it,
run the PowerShell script provided in the same directory:
Credentials are saved in
etc/settings.json in the executable directory.
This program is licensed under the GNU GPLv3 or, at your choice, a later version.