Use A4 paper by default for printing with CUPS and AirPrint

When you try to set up a self-hosted AirPrint print server with Linux and CUPS, your iPhone or iPad may only allow you to print in Legal and Letter sizes, instead of your-preferred A4.

You can set up the following steps to make sure that your iPhone or iPad uses the A4 size by default.

1. Open /etc/cups/cupsd.conf, then set or add (if not exists) DefaultPaperSize A4 (instead of DefaultPaperSize Letter).
2. Change the value on /etc/papersize to a4 (instead of letter).
3. Open your printer’s PPD file on /etc/cups/ppd, then modify the following values to A4 (instead of Letter):

*DefaultPageSize: A4
*StpDefaultPageSize: A4
*DefaultPageRegion: A4    
*StpDefaultPageRegion: A4 
*DefaultImageableArea: A4
*StpDefaultImageableArea: A4
*DefaultPaperDimension: A4    
*StpDefaultPaperDimension: A4    

1. Delete the CUPS cache directory with sudo rm -rf /var/cache/cups. Just to make sure things working right due to an old bug.
2. Try to reopen the Print menu on your iPhone or iPad.

If that is still not working

Some printers may only print A4 papers properly if the page size values are adjusted.

1. On your printer’s PPD file on /etc/cups/ppd, Change all occurences of PageSize[595.000 842.000] to PageSize[595.275590551181 841.889763779528].
2. Delete the CUPS cache directory with sudo rm -rf /var/cache/cups. Just to make sure things working right due to an old bug.
3. Try to reopen the Print menu on your iPhone or iPad.