Is it free to use the banknote exchange points?

Danmarks Nationalbank and FOREX do not charge a fee for exchanging the banknotes that will become invalid. 

If the money is to be transferred to your bank account, Danmarks Nationalbank will pay the amount 1 to 1 in Danish kroner without charging a fee. However, be aware that in some cases your local bank may charge a fee for receiving the money, which is not covered by Danmarks Nationalbank. The amount received may therefore be minus any fees from your own bank.

When transferring to a foreign account, the amount will be converted to a currency other than Danish kroner, which may incur an exchange fee. The exchange fee is not covered by Danmarks Nationalbank.