In short
This tool fills in a PDF form with interactive fields (AcroForm) online: an administrative application, a registration form, a declaration to send back. The fields appear directly on the pages: text boxes, tick boxes, radio buttons and choice lists. Save a PDF whose fields can still be edited, or flatten it if the answers must no longer change. Signature fields and buttons are not filled in, and an XFA form only opens if it also contains an AcroForm version. A PDF without fields, just a picture of a form, is better completed with “Sign a PDF”, which lets you add text to it. Your answers are written only into the downloaded file, on your device.