How to add a checkmark to a PDF form on iPhone

Someone’s emailed you a form with a row of little empty boxes: ☐ Yes ☐ No, or a consent list where each line needs a tick. On a laptop you’d click. On a phone the boxes are three millimetres wide, and a fingertip is not three millimetres wide.

Here’s how to mark them cleanly, starting with the options that cost nothing.

First: tap the box. It might be fillable.

Before you annotate anything, open the PDF and tap directly on an empty checkbox. If a tick appears — or a keyboard pops up on the text fields — you’ve got a fillable PDF with real interactive form fields, and you don’t need any of the rest of this page. Tap each box, type in the text fields, then share it back.

Fillable forms usually come from HR systems, government portals, insurers and modern lease software. Most documents in the wild are flat — scanned, printed-then-photographed, or exported without form fields — and nothing will happen when you tap. It takes one second to check and it can save you the whole exercise.

Free option 1: iOS Markup

If the PDF is open in Files, Mail or Photos, Markup can put a mark in the box. There’s no dedicated “checkmark” button, so you have two routes:

Draw it with the pen.

Tap the Markup (pen tip) icon.
Pick the thin pen and a black or dark blue ink.
Pinch to zoom right into the box — this is the whole trick. At page zoom your finger covers the target; at 300% you can land a tick inside a tiny box on the first try.
Draw the tick. Tap Undo and redo it if it sprawls outside the box.
Done → save or share.

Or type it as text.

Markup → + → Text.
Delete the placeholder and type a tick character. The quickest way to get one: hold the globe/emoji key and search check, then pick the plain ✓ — not the green ✅. The green one is an emoji, it renders in colour, and it looks obviously pasted-on next to black print.
Size it with the aA control so it fits inside the box, then drag it into place.

Both genuinely work and cost nothing. The catch is repetition: a consent form with fourteen boxes means fourteen hand-drawn ticks that all look slightly different, or fourteen new text boxes to create, resize and position. It’s the same reason filling out a whole form on iPhone with Markup alone gets tedious well before the signature line.

Free option 2: Preview on a Mac

If the document is already on a Mac, Preview is more comfortable for a long form: Tools → Annotate → Text for a typed ✓, or Annotate → Sketch to draw one. You can copy a placed checkmark and paste it repeatedly, which is the closest thing to a reusable mark that Preview offers. Export as PDF when you’re finished.

Free option 3: a form-filling app with a real checkmark tool

Some free PDF apps (Adobe’s Fill & Sign among them) carry an explicit checkmark tool — you tap a ✓ button, then tap each box. If you’re filling one long form once and don’t want another app on your phone afterwards, that’s a perfectly reasonable answer, and we’d rather tell you than pretend it doesn’t exist.

Doing it in Signed

Signed treats the checkmark as a droppable element, in the same tray as your signature:

Import the PDF — from Mail, Files, Photos, or any app’s share sheet.
Tap Checkmark, then place it on the first box. Drag once to size it to the box.
Repeat down the form. The size sticks, so every subsequent tick matches the first — no redrawing, no fourteen slightly different ticks.
Add the other fields the form asks for: text, your date, initials, printed name, and your signature from your saved library.
Export a flattened PDF and send it back.

Everything happens on the device, so a form carrying your address, salary or medical details is never uploaded to a server.

Getting the marks to look right

Whichever tool you use, these are what separate a filled form from an obviously phone-edited one:

Read what the form asks for. Some say tick, some say mark with an X, some say initial each box. An X where a tick was requested is usually fine; initials where an X was requested is not. If a box needs initials rather than a mark, that’s a saved initials stamp, not a checkmark.
Keep it inside the box. A tick spilling across two options is genuinely ambiguous, and a form processor will either guess or send it back.
Match the ink. Black or dark blue, the same colour as your signature. A red tick next to a black signature reads as two different events.
Don’t oversize it. The mark should be roughly the height of the box, not the height of the line of text next to it.
Only tick what applies. Leave the boxes that don’t apply empty rather than crossing them out, unless the form explicitly says to strike through unused options.
Check every page. Multi-page forms hide boxes in the small print at the back — scroll the whole document before exporting, the same discipline that catches a second date field on an addendum.

If the box is genuinely too small to hit

Two fixes, in order. First, zoom further — Markup keeps drawing accurately at high zoom, and it’s the difference between a tick and a scribble. Second, if the scan is so low-resolution that the boxes blur, place a small typed ✓ as text instead of drawing: a text mark is crisp at any resolution and doesn’t inherit the fuzziness of the underlying scan.

One honest note on forms

Signed is a tool for filling and signing PDFs, not a source of legal advice. Ticking a consent box is you agreeing to something — read the line next to it before you mark it, especially on anything with money, medical care or a deadline attached. If a form is consequential and you’re not sure what a clause commits you to, ask the sender or take proper advice; that’s cheaper than an unticked box you meant to leave unticked.