You cannot combine requests for electronic and wet signature in the same envelope. You also cannot force a wet signature when sending documents from the web app. If you've enabled the option, your recipients can choose to print and sign documents, then scan them back into DocuSign. But they would need to do all electronic or all wet signature.

You might want to include the recipient in the envelope workflow twice with different signing order each time. The first time, you would assign all the electronic signature fields on the document to that recipient. For the second time the recipient is asked to sign, provide a Private Message explaining how they should use the Print and Sign option to wet sign and scan in the required document.

Via the API, your application can send documents and require the signer to only print and sign.