Example:

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

// Adding a simple shape with absolute size and position.
Shape shape = builder.insertShape(ShapeType.RECTANGLE, 100.0, 40.0);
// Set WrapType to WrapType.None since Inline shapes are automatically converted to absolute units.
shape.setWrapType(WrapType.NONE);

// Checking and setting the relative horizontal size.
if (shape.getRelativeHorizontalSize() == RelativeHorizontalSize.DEFAULT)
{
    // Setting the horizontal size binding to Margin.
    shape.setRelativeHorizontalSize(RelativeHorizontalSize.MARGIN);
    // Setting the width to 50% of Margin width.
    shape.setWidthRelative(50f);
}

// Checking and setting the relative vertical size.
if (shape.getRelativeVerticalSize() == RelativeVerticalSize.DEFAULT)
{
    // Setting the vertical size binding to Margin.
    shape.setRelativeVerticalSize(RelativeVerticalSize.MARGIN);
    // Setting the heigh to 30% of Margin height.
    shape.setHeightRelative(30f);
}

// Checking and setting the relative vertical position.
if (shape.getRelativeVerticalPosition() == RelativeVerticalPosition.PARAGRAPH)
{
    // etting the position binding to TopMargin.
    shape.setRelativeVerticalPosition(RelativeVerticalPosition.TOP_MARGIN);
    // Setting relative Top to 30% of TopMargin position.
    shape.setTopRelative(30f);
}

// Checking and setting the relative horizontal position.
if (shape.getRelativeHorizontalPosition() == RelativeHorizontalPosition.DEFAULT)
{
    // Setting the position binding to RightMargin.
    shape.setRelativeHorizontalPosition(RelativeHorizontalPosition.RIGHT_MARGIN);
    // The position relative value can be negative.
    shape.setLeftRelative(-260);
}

doc.save(getArtifactsDir() + "Shape.RelativeSizeAndPosition.docx");