See this: https://support.mozilla.org/en-US/kb/fix-printing-problems-firefox#w_reset-all-firefox-printer-settings

Reset all Firefox printer settings

Not helpful to me as I am a PC Dummy & do not want to make changes when message says "This might void my warranty". Attaching copy of print from Mozilla Firefox......Internet Exployer prints correctly but I've preferred Firefox ever since I learned of it.

Hi Janet, the about:config preferences editor lists a lot of settings. If you were to change some of those, Firefox might stop working correctly. But in this case, you are going to reset certain print-related settings, which will force Firefox to requery Windows for information about those printers. This is quite safe.

Anyway, here's my usual spiel on this problem:

If Firefox is not using the whole sheet of paper, or otherwise misunderstands what is contained in your printer's paper tray(s), that can be caused by Firefox having extracted the wrong paper size settings from Windows when reading the print driver data. Clearing it involve some heavy clicking:

(1) In a new tab, type or paste about:config in the address bar and press Enter. Click the button promising to be careful.

(2) In the search box above the list, type or paste print and pause while the list is filtered

(3) For each setting that specifically mentions the problem printer, right-click and Reset it. The fastest way is to right-click with the mouse and then press the r key on the keyboard with your other hand.

Here's a possible shortcut: In a couple threads involving printouts that used a small portion of the page (on Brother printers), the preference printer_printer_name.print_paper_data was set to 256 and when the user edited it to 1 that by itself fixed the paper size problem. If you use a Brother printer and see something other than 1 there, you can edit the value by doubling-clicking it or using right-click>Modify to see whether 1 is the number you need.

Sir, This might be helpful but haven't tried yet......wanted to let you know I have an HP Office Jet 3830 printer and it is great with my Windows XP but not this crazy Windows 10. Should I go ahead and try what you have mentioned above (Brothers Printers)? Really appreciate your help.

Hi Janet, try the numbered steps first, since I don't know the best number for the print_paper_data on an HP. You certainly could compare what shows up on your other computer to see if there's a difference.

is this what you are referring to on my HP printer?

print.printer_HP_OfficeJet_3830_series.print_paper_data;141

Hi Janet, do both computers have that same value? If so, the problem is likely with one of the other preferences.

Windows 10 has Value 141

Windows XP has Value 1

Hmm, sounds like it's worth trying 1 on the Windows 10 computer!

jscher2000

Appears you have solved my problem. Thanks so very much for your time,