You could put your text/graphics into a table consisting of one column and
one row. In Table Properties, specify that the table width will be whatever
your line width is, let's say 6.5 inches where you have a 1 inch Left and
Right Margin. As you fill the Table with more text/graphics, it will fill
the page. There is a choice in Table Properties, Borders and Shading for a
very light, greyed out line that will be the border of your table. This
would give the effect of a greyed out border around the page, in the same
location as the margins of the page. A Page Border falls inside the margins
that have been set for the document or section, so it does not mimic the
actual margins set in Page Layout. What is it that you are trying to do with
the "imaginary" margin lines?
