Yes, you can allow donors to pay your processing fee on their online donations. 

Simple Page Designer

To turn this feature on for a page created using the Simple donation page setup, go to the Donation Page Settings tab. Under the Donation Options area, turn the toggle Allow to pay processing fees to YES. You can choose the sentence to describe this and you also have the option make this selection default or required. With it set to default, the donor would need to uncheck the box to remove the processing fees from the charge.

Advanced Page Designer

In the Advanced Page Designer process, you can activate this option by clicking the three dots on top left side of your payment widget. Click on Widget Settings, and then in the Settings tab you can activate it by setting Allow to pay the processing fee to YES. You can also choose the sentence and default or required options.