View.ReadingLayoutTruncateMargins (Word)

Returns or sets a WdReadingLayoutMargin constant that represents whether margins are visible or hidden when a document is viewed in Full Screen Reading view. Possible return values are wdAutomaticMargin - Shows the pages without margins, wdFullMargin - Shows the pages with margins, wdSuppressMargin - Microsoft Word determines automatically whether to show or hide the margins based on the available space.

ActiveWindow.View.ReadingLayoutTruncateMargins = wdAutomaticMargin