​@IwanRW 

Why reinvent the wheel when this is already available? You can simply share the following guide with steps on how to set up their signature within the Docusign account ahead of signing a document.

Docusign Support article check “Change signature in account: Manage Profile”

Hello Michael, 
Thanks for your reply!
Unfortunately, our users do not have Docusign's user login and only interact within our application (Embedded Sign). Is there any solution for this? or just practically impossible?

Thank you.

The embedded signer can use the signature that was used previously during signing through the "Adopt your signature" modal if they have the same combination of email, name, and clientUserId. If one of the values is different, the Docusign system regards it as a different embedded signer, thus the previously used signature won't appear on "Adopt your signature" modal. 

For the application developer, you would need to manage the combination of email, name, and clientUserId in your database and use the same combination when you send the envelope to the same embedded signer if you want the signer to see the previously used signature during signing.

Adopt Your Singature: https://support.docusign.com/s/document-item?language=en_US&rsc_301&bundleId=yca1573855023892&topicId=dga1573854990297.html&_LANG=enus