Putting form element by text anchor

Hello Everyone!

In the API Documentation of Adobe Sign we see only the change to give a location for FromField using page numbers and pixels:

In our system we do not know the exact position, because it's a web-based system. Is there a way to position placeholder (form element) giving a kind of "Text Anchor"? For example saying the field element should be located after "Signature 1:" text in the PDF document?