The Sign program is compatible with the following versions of Mathcad: Mathcad 14.0 M030 and Mathcad 15. If these versions can be installed on Windows 10, then you will be able to run it on Windows 10.
I've searched for the necessary data and found out that Mathcad 15 is compatible only with the following versions of Windows: Windows 7 (64- or 32-bit), Windows Vista (64- and 32-bit), Windows XP Professional (including 64-bit), Windows XP Home.
As you can see, there is nothing mentioned about Windows 10, but users reported that you can actually install it. Make sure to download the latest version and it will install just fine, then the Sign program can be used as well.
Here are the resources you need:
Note: The files are in the XMCD format, therefore you have to load them into Mathcad. Just read the Documentation to learn how to do that. It's a folder found inside the archive that you downloaded from the second website.