Default Scale Pictures in Nexus 5

I have an HP Photosmart Premium inkjet printer that connects to my Nexus 5 very well with Bluetooth and with the HP Print Service Plugin. what I'm having trouble printing is printing to 4x6 paper. Does anyone know how to scale photographs to print to 4x6 paper? When I select 4x6 paper, the pictures get cut off. Printing on Letter size paper prints fine.