How to fill a PDF form on iPhone, even one that isn’t fillable

Step 1: is the form fillable?

Open the PDF from Files (save it there first from Mail or Safari with the share button › Save to Files). Tap where you’d write your name:

• A keyboard appears: the form has fields. Fill them one by one.
• Nothing happens: it’s a flat PDF, a picture of a form. Go to step 3.
• The page says “Please wait…” and something about the viewer: it’s an XFA form. Go to step 4.

Step 2: fill it with the free tools in iOS

Since iOS 26, iPhone has a Preview app, like the Mac’s, that opens PDFs, fills forms and offers AutoFill with your contact details. The Files app’s Quick Look view also lets you add text and a signature with Markup. Tap each field, type, and use the arrows above the keyboard if they appear.

Things to watch:

• Dates: type them in the format the form shows. Some fields reject anything else silently.
• Totals: forms made in Acrobat often calculate sums with built-in scripts that most iPhone viewers don’t run. Check that totals actually update; if not, add them yourself.
• Checkboxes: tap once; a second tap may untick.

Step 3: forms without fields

Use Markup’s text tool (the “+” button › Text) to place text boxes, and drag each onto its line. It works, though lining up a dozen boxes on a phone is fiddly. Apps with a “Fill & Sign” mode make this faster by snapping your text to the nearest line or box at a size that fits.

Signing: Markup’s “+” › Signature adds a drawn signature. That’s a picture of a signature, which is fine for most forms. If the form asks for a digital or certificate signature, see signing with a certificate on iPhone.

Step 4: the “Please wait…” forms

Some government and corporate forms use XFA, an older Adobe form technology. Viewers that don’t support it show a “Please wait… If this message is not eventually replaced…” page instead of the form. You need an app that supports XFA, or ask the sender for a regular PDF version. Many agencies offer one.

Step 5: send it so your answers arrive

1. Save first. Then share the saved file, not a screenshot.
2. If a portal rejects fillable PDFs or the answers disappear on the other side, send a flattened copy, where answers become part of the page. Keep the fillable original.
3. Check the size: most email accounts take 20 to 25 MB, many portals 2 to 5 MB. How to shrink a PDF.
4. If the form was already signed by someone, make sure your app doesn’t break their signature when it saves. Here’s why it can.