Based on my previous question Fill out field for pdf revision when signing with PDFbox I was able to fill out the PDF field with a valid signature:
When looking at a signed document from AdobeSign they managed to group the fields like:
I am not able to analyse the created document von Adobe since they locked it at the end with a password. Is this to make sure nobody is able to edit the forms after the signature (I know that the signature is not valid anymore after somebody did it, but it reduces the risk of a user by accidentally writing into the field.
Update:
setting two signatures works and it will set the form fields in. But only for the Field 2, not the Field 1 from the first signature. see: https://file.io/cvHSBqRzXPyH


