That's not possible via Airprint. If Epson has an own app that works with your printer, you might be able to change the size, or whatever is allowed there.
Hi Nael - I'd have to completely agree w/ Johanna, i.e. once a 'job' is sent via AirPrint to your printer there is no control over the settings you want to possibly alter; however, please explain from which app(s) you are sending these print jobs - you should have some control w/i an app, such as Pages that the Epson will recognize - SO, let us know what you are trying to do and what apps you are using - Dave