It really would depend on the type of voucher you have. All vouchers are transferable but some may require the person named on the voucher to be present at ticketing. And no this will not result in any extra fees. If a fully refundable ticket is issued with a voucher, only the additional collection is refundable, not the $150 original voucher amount.

If the voucher is a delta dollars voucher then travel must originate before the expiration date. If it is a transportation credit voucher then you must issue a ticket before the expiration date but the ticket is then good for 1 year from the date of issue of the ticket.

Hope this helps.