Describe each field as name@page:x,y,w,h in PDF points and KukPDF adds an empty AcroForm text field at that spot. It creates text fields only.
Your file is processed in your browser and is not uploaded to a Kuklabs server. The page does contact Kuklabs to check your plan, without sending the file.
Text fields only.
It is skipped without an error. Use the name@page:x,y,w,h pattern, for example full_name@1:72,700,200,24.
PDF points, where one point is 1/72 of an inch.