Finding every field with the form fields panel in PDF by Zaweba
The form fields panel in PDF by Zaweba lists every field once, with page, kind, value and flags, so you can find the empty required ones and fill them.

Long forms hide their gaps well. A twelve page application can have one required box tucked at the bottom of page nine, and you only find out when somebody sends it back. The form fields panel in PDF by Zaweba is there so that never has to happen: it lists every field in the document once, in one place, and lets you jump straight to any of them.
Each row in the panel tells you the page the field is on, what kind of field it is, the value it holds right now, and whether it is marked Required or Read-only. That is enough to see the whole form at a glance without scrolling through every page looking for boxes.
What the panel shows you
Think of the panel as the form turned into a table. Text boxes, check boxes and the other kinds of field each get a row, so a form that looks busy on the page becomes a simple list you can read top to bottom. The value column is the useful part. A field that is still blank stands out, and a field with the wrong thing in it is easy to spot because you are reading values side by side rather than hunting for them on the page.
The Required and Read-only flags matter as well. Required tells you the form's author expects something there. Read-only tells you the field is locked, so there is no point trying to type into it, and if it holds the wrong value the fix has to come from whoever sent you the form.
Searching and filtering
A search box sits at the top of the panel. Type part of a field's name or what you expect it to contain and the list narrows down. On a form with hundreds of fields this is the quickest way to find, say, every field to do with an address or a date.
The filter for required fields still empty is the one most people come to love. Turn it on and the list shows only the fields the form needs that you have not filled yet. Work down that short list and when it is empty, the form is complete as far as its author defined it. It is a far better final check than reading every page again.
Going from the list to the page
Click a row and the document moves to that field, ready for you to type in it. You do not need to find the page, zoom in or aim the mouse at a small box. Click, type, click the next row, type again. For forms you fill often, this turns a slow job into a quick one, because the panel becomes your route through the form rather than the pages themselves.
It also helps with forms that are badly laid out. Some PDFs have fields in an order that makes little sense on screen, or boxes so small they are hard to click. Working from the panel sidesteps both problems.
How it fits with the rest of the forms tools
The panel is for filling. When you are making or changing a form instead, Form, then Prepare form is where you add and edit fields, and the panel is still a handy way to check what is there afterwards. If you have the values in a data file already, importing that data fills the form in one step, and the panel then shows you what came in and what is still missing. And if a form needs starting again, Reset form and Clear form sit alongside.
Where people slip up
Don't treat an empty required filter as proof that the answers are right. It only tells you every required field has something in it. Read the values column once before you send the form off.
Don't assume a field missing from the Required filter is optional for the person receiving it. Plenty of forms never mark anything as required, even when the organisation expects every box filled. The flag is only as good as the form's author made it.
And remember that Read-only fields cannot be changed by typing. If one holds a wrong value, ask the sender for a corrected form rather than trying to work round it.
Used this way, the form fields panel in PDF by Zaweba takes the guesswork out of long forms, and it all happens offline on your own PC.