If I have a Delta voucher in my name, can I give it to another person to use, for example to my daughter?
From a paper voucher ....
Redemption/Transferability: Voucher is non-transferable unless assigned to someone traveling with the original voucher owner on the same reservation at the time the voucher is being redeemed.
In other words it can be applied to your daughter's airfare, as long as she is traveling on the same reservation as you are.
If I have Delta voucher on my name, can I give it to other person to use, for example to my daughter?
No. "All tickets are non-transferable per the fare rules. Name changes are not permitted."