Go to Settings > Pricing > Adders. If the adder is not in use, use the dropdown under Status to change from Active to Draft or Archived.
If the adder cannot be archived because it is being used by a pricing model, follow these steps:
Click Settings > Pricing > Pricing Models. Click into the pricing model(s) the adder is being used by.
Click the x next to the adder. This will remove the adder from the pricing model.
Save changes.
Return to the adder page by clicking Settings > Pricing > Adders and use the dropdown under Status to change from Active to Draft or Archived.