Currently, PDF receipts in Luminate Online have many possible input fields implemented, but to my knowledge, not yet one for Gift Designation, a data point that does appear when you look at the gift in the Interactions tab.

Source: https://webfiles-sc1.blackbaud.com/files/support/helpfiles/luminate-online/help/luminateonline.html#../Subsystems/Setup/Content/Ref/Admin_Receipt_Manager_PDFReceiptInputFields.html

This would allow staff and donors to see the gift designation on PDF receipts, and both have requested this common-sense feature.