Either the form has no real fields — it is a flat page that only looks like a form — or it is an XFA form only Adobe’s software can fill, or it is open in a read-only preview. Save it to Files and open it in Fill PDF Form in Safari: it lists the fields it finds and flags XFA forms.
Runs in this tab, on pdf-lib and pdf.js, so your file is read from your own device and never sent anywhere. Check it yourself
How do I fix it?
1Save the PDF to FilesUse the share button and choose Save to Files, so you are working on a real copy rather than a preview.
2Open it in Fill PDF FormIn Safari. Every field is listed with its label and page number, which is far easier on a phone screen than tapping tiny boxes.
3Fill, tick and lock it inType the answers, tick the boxes, and turn on Lock the answers in if the form is going to someone who shouldn’t change them. Save the copy.
4No fields? Type on the page insteadFor a flat form, use Edit PDF’s Add text tool to place your answers on the lines, or Markup’s text box in the Files app.
5An XFA form? Use Adobe’s softwareXFA forms can only be filled in Adobe’s own apps; Adobe Acrobat Reader on a computer is the dependable route. Or ask the sender for an ordinary PDF version.
Why does this happen?
It has no fields. Many “forms” are a scanned or printed page with lines and boxes on it. There is nothing to tap into, because nobody ever made the boxes into fields.
It is an XFA form. Forms built with Adobe LiveCycle, common on some government sites, are a different kind of PDF. Apple’s viewer and most browsers show a “Please wait…” message or a blank page instead of the form.
It is open in a preview. A PDF tapped inside Mail, WhatsApp or a web page often opens in a quick preview that doesn’t keep what you type. Saving it to Files first gives you the full viewer.
Form filling is restricted. An owner password can mark form filling as not allowed. The form opens, but the fields refuse to change.
Questions
How do I fill out a PDF form on my iPhone for free?
Save the PDF to Files, open Fill PDF Form in Safari and add the file. Each field is listed with its label; type your answers, tick the boxes and save. Nothing is uploaded.
Why does my PDF form say “Please wait…” on iPhone?
It is an XFA form, which only Adobe’s software can display and fill. Use Adobe Acrobat Reader on a computer, or ask for an ordinary PDF.
Why can’t I type in the boxes?
The boxes are probably printed lines, not fields. Add your answers as text with Edit PDF, or with Markup in the Files app.
Will my answers disappear when I send it?
Not if you lock them in. Some viewers don’t show filled fields; flattening the answers into the page makes them visible everywhere.