Ms word problems

hi was wondering if anybody could help me. i have been asked to create a booklet in word, i have followed the instructions i have been given. i have been asked to create the booklet in a3 i have my page to landscape, but when i change the page to a3 i get a message saying " one or more margins are set outside the printable area of the page. choose the fix button to increase the appropriate margins" and there is a fix button and ignore. i click fix and i cannot use all the page i click ignore and nothing happens.

i would be very greatful if someone could help me thanks

You should check the page setup for all sections of your document, chances are one or more are different, hence the margins message.