This is not possible at this time. You can only stamp values of radiobutton and checkbox on PDF.

Thanks for suggesting this feature. Please add this to our Community Ideas

We cannot estimate when your feature request will be available; but, we periodically review the list and add new features to the product roadmap.

We would recommend joining the mailing list on our Company News page so you're updated when a new update is released. 

An immediate hotfix might be available under our Premium Support if you're willing to sponsor the development.