Inuit Link does not have this specific functionality built in (except for ProConnect Tax Online) but here is how it could work:

1. Click on the Add request button on the Client Details dashboard for the relevant tax year;
2. In the pop-up, choose a Request Type (other than Engagement Letter and enter a description under Request Text for what your client should do with a copy of the return.  I would suggest using either "Yes/No Answer" or "Open Ended Answer" to request an acknowledgement from your client (note: you can do the same for F.8879, if applicable);
3. Click on the paper clip button for Attach file(s) and select the return which you should have saved from PS in PDF format (the PDF does not need to be encrypted separately since Intuit Link itself is already encrypted); and
4. Click on the Save button.

If you are using eSignature, you should refer to the instructions in this article instead:

https://proconnect.intuit.com/community/manage-integrations/help/how-to-use-esignature-in-proseries-...