Print from iPad to airprinter

Trying to print (for example) a pdf attachment from email Printer is a Canon MG5650, Same problem occurs with my iPad mini and father's older iPad - both have iOS 9.3.2

When I select print, the options window opens and the correct printer is located. The only options available are range (of pages), double-sided, and black &white. The page size is set at 3 x 5 1/2 inches and cannot be changed. Apple customer support told me there is no way to change the default paper size on the iPads (why is default not A4??) They suggested that I probably need an app from canon to make this work properly.

Canon support suggested I try the CanonPRINT Inkjet/SELPHY app. I got it but had to save the pdf I wanted to print first, and then use the app to print the saved file. I managed to acheive an A4 print out of one page of a two page document - but the second page never appeared. . Canon say they can't help as this is an apple issue....

The printer is working without problem via my pc running windows. I can print the same pdf document onto A4 paper - and I can select the paper size if i want to change it.

Any ideas please?