On the BN, left and right margins are set in Document Layout, and top and bottom margins are set in Page Settings. Move to the top of the Braille document before changing them. Enter Document Layout with [BACKSPACE with L], [CONTROL with L] and Page Settings with [BACKSPACE with P], [CONTROL with P]. Change the appropriate settings in the usual way, and if you want these to be the default margins for all subsequently created documents, press [BACKSPACE with S], [CONTROL with S] from both within Document Layout and Page Settings. You'll see "Default Set" displayed to confirm this. Note that if you erase this file, the margin settings for all subsequently created documents will revert back to the last settings saved.
HTH, Maria
