Comment 37 for bug 29622

It looks at this point like there's some confusion in Firefox, probably in other
gekko-based browsers, with regard to where and to which printers page settings
apply. It's not obvious that the page settings are actually per-printer, and
stored as such in prefs.js, even though there's a set of "global" settings which
aren't per-printer but seem to have no effect. These are probably defaults for
newly discovered printers.

You can see this by going to file-print, selecting a printer, and then
cancelling the print operation, then going to page setup and checking the page
settings. Change the settings, go back to file->print, select another printer
and cancel. Then go back to page settings and your previous settings have been
"forgotten". Actually, they're associated with the first printer you selected,
and stored in prefs.js (accessable through 'about:config') with a spec for the
printer.

The quick fix is to either edit prefs.js or use about:config to do the same,
keeping in mind that some settings don't seem to show up there until they've
been changed for each particular printer.

Filter on margin (you can do the same for header and footer). You'll see lines
in about:config like

print.printer_PostScript/some_printer_name.print_margin_top

same for print_margin_bottom, print_margin_left and print_margin_right.

Once you edit the proper entries, they should 'stick' between invocations of the
browser.

The larger fix seems to be that the page setup UI is going to have to be
redesigned - proper labeling, moving the config UI or whatever - so as to
clearly associate a particular page setup with a particular printer. Either
that, or the page setup is going to have to be generalized so that there's a
single master setup not linked with any particular printer, as implied by the
present UI layout.