LeftIndent

public double LeftIndent { get; set; }

Document doc = new Document();
DocumentBuilder builder = new DocumentBuilder(doc);

// Below are two ways of aligning a table horizontally.
// 1 -  Use the "Alignment" property to align it to a location on the page, such as the center:
TableStyle tableStyle = (TableStyle)doc.Styles.Add(StyleType.Table, "MyTableStyle1");
tableStyle.Alignment = TableAlignment.Center;
tableStyle.Borders.Color = Color.Blue;
tableStyle.Borders.LineStyle = LineStyle.Single;

// Insert a table and apply the style we created to it.
Table table = builder.StartTable();
builder.InsertCell();
builder.Write("Aligned to the center of the page");
builder.EndTable();
table.PreferredWidth = PreferredWidth.FromPoints(300);

table.Style = tableStyle;

// 2 -  Use the "LeftIndent" to specify an indent from the left margin of the page:
tableStyle = (TableStyle)doc.Styles.Add(StyleType.Table, "MyTableStyle2");
tableStyle.LeftIndent = 55;
tableStyle.Borders.Color = Color.Green;
tableStyle.Borders.LineStyle = LineStyle.Single;

table = builder.StartTable();
builder.InsertCell();
builder.Write("Aligned according to left indent");
builder.EndTable();
table.PreferredWidth = PreferredWidth.FromPoints(300);

table.Style = tableStyle;

doc.Save(ArtifactsDir + "Table.SetTableAlignment.docx");