Two very different documents get called forms. One has real fields built into it — click and type. The other is a printed layout with lines drawn on it, which needs text placed on top. This handles both, and the difference decides what happens when you type.
For a real form, the fields are found and highlighted, and the count is stated up front: how many blanks, and how many of them the form actually requires. Tab moves through them in reading order, which is right almost always. On a computer, the list beside the document doubles as a progress view — click a row to jump to that field.
Nothing is marked as a problem until you press Download. Flagging every empty box the moment the document opens is a common pattern and a bad one: it turns a form into a wall of red before you have done anything wrong. The check belongs at the end, and at the end it names exactly which needed answers are still blank — then lets you download anyway, because sending an unfinished form is a normal thing to do.
The last question is the one most tools bury under the word “flatten”. Do the answers stay editable, or not? Framed properly it is easy: permanent if you are sending it off as final, still fillable if someone else has to add their part. That is a question about who gets the document next, so that is how it is asked.
One honest caveat, named rather than discovered: a form with automatic calculations does not compute here — your answers are kept, but the totals stay as they were, and the field says so rather than letting you assume. The older XFA kind of form is declined with a plain explanation, because half-filling one of those is worse than a clear refusal.
On a phone the same fields stay tappable — zoom the page to a comfortable size and type. A dedicated one-field-at-a-time flow for small screens is still on the roadmap; signing with a saved signature and downloading are not.