Hello,
Using HTML Extended available in Premium licenses you can set fixed location on pages to images from HTML using phpdocx_image tag and data-relativeToHorizontal and data-relativeToVertical attributes.
addImage method includes the same options in all methods (relativeToHorizontal and relativeToVertical). In the package you can find a sample that illustrates both options (Core/addImage/sample_5.php).
Regards.