More details and info are needed about the .pdf form and the website.
Is it an online pdf (accessed via web browser) or has she downloaded it and is using a pdf program on her pc?
Is she logged in on the website that has the online pdf form and is she opening it from there? There must be some sort of a login password or she would not have been able to save it at regular intervals.
That begs the question of how she saved it at regular intervals and then was able to go back to it to continue filling it in. Please tell us how she was able to do that.