Acrobat Pro isn't saving fillable fields after changes in Prepare a Form

I am double-clicking on the box in the PDF after hitting "Prepare a form"- where Adobe has created fields for me (they look great!) but the text in the firlds is random/ incorrect. Once you double-click, a pop-up opens and you'll add what you want the field to say. These fields seem to save in the dialogue box running along the right-hand column; my changes are reflected there. I also have watched several videos and that apprears to be all I need to do! However, when I open my PDF after changing all these fields, no changes are reflected. There is no step I appear to be missing in any videos I've watched- totally stumped!