The main question you should ask yourself is whether the signature should be proof for a legal document. If that is the case, most auditors will require additional information, such as an audit trail. The solution you mentioned, Docusign, or Adobe Sign provide this.
If you just want a user to be able to use a widget to create a signature, you could use something like this: https://marketplace.mendix.com/link/component/107984
Kind regards, Bart van den Heuvel