Open Print-ready from the Home screen (or use its own page link).
Tap Choose file and select your PDF from the phone or computer.
Choose the Paper size (A4, Letter, Legal or A3) that your printer uses.
Set the Margin (None, Small or Normal). Tick Page numbers or Remove blank pages if you need them.
Tap the big purple Start button and wait a few seconds.
When you see Done!, tap Download. The new file is saved on your phone or computer.