@Antoni_oni I know of no functionality that is present in DocuSign that allows you to disable any screenshots that can be taken of the document. DocuSign runs in the cloud and is browser based so I do not believe there is anything that could be present within DocuSign settings to remove screenshotting from a browser. There are also hundreds of other products that can take screenshots via an application like the Snipping Tool or Lightshot.
Also note that if the Recipient has a DocuSign account they can always view that document. They also via the completion notification of the envelope can download the document from the envelope.