I do not know the answer, but I am not even sure what it is that you are asking.

Are you talking about the display on your computer, or are you asking about the printouts.

Are you referring to pages generated by some arbitrary website and not something you are producing yourself ?

I was asking about printouts. Let me explain you. I'm working on a web application that generates pdfs and you can print them directly from browser. But In Firefox there is a problem because . When I click the print button the print window open ( FIREFOX PDF VIEWER WINDOW) and if I print with default settings it prints the document on letter, because that's the default setting, and I need to print that on a A4. Or this is a setting for every with a printer that will have to made or I can set the default to A4 somehow ? Thank you and sorry for my English.

I admit I do not know the answer, but I suspect that whilst you may define the pdf size you may not be able to change the user's print settings.

I would also point out that in practice individual users may have only one size of paper loaded in their printer. In Europe even in a commercial office it is probably almost universal to have A4 available but it is probably extremely rare for even printers with multiple size paper to include American/imperial letter/foolscap sizes.

You may get someone knowledgeable give you an answer here but there are possibly better places to ask. Try for instance

• https://forums.mozilla.org/addons/viewforum.php?f=7
• http://forums.mozillazine.org/index.php

Thank you.

If you do ask elsewhere and get an answer resolving this post back here as the information may help others with the same problem.

I will . Thanks