Question: AirPrint iOS V11
When using AirPrint with iOS V11 to my HP Officejet Pro the output on A4 paper comes out at 3 1/2 x 5 inches by default more often than not!
This problem occurs with Mail and Safari. If I wait 20-30 seconds after selecting the printer to use the image of the output in the preview screen will often change in size? If I try to use the App Switcher option having started the print job I cannot always get to see the 'print job' window? When I do see the job I notice the 'Options' size is set to 3 1/2 x 5 inches just like like your example in 'Use of AirPrint' facility at support.apple.com/en-ghHT201387.
In summary it appears very hit and miss getting the print job to use A4 size when printing!
This problem doesn't occur when using other many other apps to print pages (e.g. iBooks).
This problem did not occur when I had iOS V10 on my iPhones and iPad.
This problem has been blamed on HP AirPrint support but I feel my experience as described above indicates that iOS V11 is partially to blame.