API reference / Common / Engine types / PageMargins
Interface: PageMargins
A section's page margins (w:pgMar, CT_PageMar), in points.
DOCX stores these in twips; converted to points at import. top/bottom may be negative (content bleeding into the margin). header/footer are the distances from the page edge to the top of the header / bottom of the footer. gutter (the extra binding margin) and mirror margins land when a real case needs them.