PdfHtmlHeaderFooterReserveSpaceAlways Property

If true, space is reserved on all pages regardless of header and footer visibility. This is the default behavior. If false, space for the header or footer is reserved only on pages where they are actually rendered, and styling rules intended for print layout will be applied in this case. It is ignored if ShowOnlyInHtmlToPdfPages is explicitly set to false. The default value is true

public bool ReserveSpaceAlways { get; set; }