You can input barcode with both Typewriter tool and edit text tool as long as barcode font was installed.
Use Typewriter: Choose Typewriter under Comments menu, click on anywhere you want to input barcode, select barcode font available in the list, input code you need.
Use Edit text tool: Go to Edit Object->Text under Edit menu of Foxit PhantomPDF, double click on anywhere you want to input barcode, select barcode font installed on system, input code you need.