Legend Element
Available in DocX, PDF and Image templates.
The legend is a printable representation of the Key that appears on the Map tab. It should look more or less the same but without the user interface elements such as hyperlinks and checkboxes.
In PDF and Image templates.
In DocX templates.
Legend properties window gives you control over the layout of map legend entries. All fields in the Legend Properties window are explained on the inner preview.
The legend properties in DocX page layout cannot configure border colour and width here. As all the placements are effectively images in the document border styling is done in Word.
This is how the Key panel looks in Print.