I'm not certain, but I think you'd resolve this by uploading the PDF to Screen 4.4.  In the "Link to Form" box, I select "Sch A - Other"

There are multiple steps to get this resolved:

1 - attach the PDF in screen 4.4

2 - select form 8283, then choose Form 8283 Donee Signature Document

3 - Activity name or number - choose the organization/entry for the donation.

If this doesn't resolve it, the incorrect Donee Acknowledgement may have been selected.