[cups] force CUPS print server to fit-to-page

[Josh]

 Greetings,

I've just set up an AirPrint server for a home office by following
instructions in

https://www.linux-magazine.com/Issues/2013/154/AirPrint-in-Linux
and
https://github.com/jpawlowski/airprint-generate

Printer works just fine except for a problem described in

https://serverfault.com/questions/897140/force-cups-print-server-to-fit-to-page-if-job-is-not-a4

Text jobs sent from iOS devices print full pages but photos and images
print size is 4x6 inches.

CUPS v1.6.3 on CentOS 7.

Does anyone have any ideas?

Please advise,
Josh.

PS. More tests and observations:

$ sudo lpoptions -o auto-fit=True

has zero effect as well as adding

Option auto-fit True

to the DefaultPrinter section of /etc/cups/printers.conf.

As a matter of fact I have an impression that all options created by
lpoptions command and stored in /etc/cups/lpoptions have zero effect.

For example

$ sudo lpoptions -o media=Letter

has no effect whatsoever but adding line

Option media Letter

to the DefaultPrinter section of /etc/cups/printers.conf has a very
noticeable effect despite the fact that Letter has already been selected in
printer settings UI.

As a side question, could anyone explain the difference between lpoptions,
printers.conf and printers settings UI?