Given a list of points:

int pageNum = 1;
PageInfo page = document.GetPageInfo(pageNum);

var ann = new FreeHandAnnotation(document.Id, page.PageId, session);

foreach (Point pt in points)
{
    if (pt == null)
        ann.AddBreak();
    else
        ann.AddPoint(new LfPoint(pt.X, pt.Y));
}

page.AddAnnotation(ann);
ann.Save();
page.Save();