Do your donors contact you for a new copy of their donation receipt? Do your accountants want copies of specific receipts? You can resend or download receipts from the Search Transaction process in Reporting.
Filter your list as normal, for exporting a report as outlined here.
If you are looking for a specific individual, you can use Search Transactions and look them up by name, email, or phone number.
On the results screen, where you would normally now export your report, in the granular review area at the bottom, find the donor and click on the Actions menu.
Here, you can automatically Resend Receipt or Download Receipt. If you resend it, you will get a confirmation screen before it will send out the email. Click OK to complete the sending of the receipt.