How to add a hanko seal to a PDF on iPhone

A form arrives as a PDF with a little circle next to your name, or a 印 mark, and the sender wants it back with your hanko on it. Your seal is in a drawer, there’s no printer nearby, and you’d rather not print, stamp and scan a page just to send it straight back.

You can do this from your iPhone with the hanko you already own. You don’t need a hanko-maker app, which designs a new seal from a template. You need a good copy of yours, placed in the right spot, in a file the recipient can’t accidentally knock it off.

There are two jobs: make a clean image of your hanko once, then place it on each PDF. A personal seal makes the first job harder than a company stamp, for three reasons. It’s small (often around a centimetre across), the red ink photographs weakly, and it’s usually placed over or right beside printed text, so any white box around it shows straight away.

1. Get a good impression on paper

Everything downstream depends on this, so spend a few minutes here:

Use plain bright white paper. Printer paper is fine. Lined or cream paper leaves marks you’ll have to clean off later.
Press on something slightly soft. A stamping mat, or a few sheets of paper or a thin notebook underneath, lets the whole face of the seal make contact. On a hard desk the edge of the circle often breaks.
Ink it properly. Tap the seal on the ink pad or seal paste a few times rather than once, then press straight down, hold for a second, and lift straight up. Don’t rock it.
Make several impressions and pick the best: an unbroken ring, every stroke filled, no doubled edge.
Let it dry before photographing. Wet seal paste is shiny and reflects light.

A faint, pink impression is the most common problem with hanko. Fix it with more ink and another press, not with an editor afterwards.

2. Capture it sharply

Because the seal is so small, sharpness matters more than usual. A blurry one-centimetre circle becomes an obvious smudge once it’s on a page.

Use daylight and turn the flash off. Flash leaves a bright spot right in the middle of the seal.
Don’t get too close. Hold the phone flat and parallel to the paper, switch to the 2× or 3× lens if your iPhone has one, and step back until it focuses. Getting very close with the wide lens tends to blur and casts your phone’s shadow on the paper. Newer iPhones may switch to macro on their own, which also works.
Tap the seal to focus before you take the shot, and take a few.
Or use the document scanner. In Notes or Files, tap the camera or ••• menu, then Scan Documents. It evens out the light very well, but it saves a PDF rather than an image, so you’ll still have to get the seal out of it as a picture. A zoomed-in screenshot works, at your screen’s resolution.

Keep the full-size original. You can crop later, but you can’t add detail you didn’t capture.

3. Crop it and remove the paper

Crop tight in Photos (Edit, then the crop tool), leaving a small margin around the circle.

Then remove the white. A photo of a hanko is a red seal on a white square. Put that on a form and the white square covers the printed name or the 印 circle underneath, which is exactly where a personal seal is supposed to sit. What you want is a transparent PNG with only the ink kept.

Free ways to do it:

Lift the subject in Photos. On recent iOS versions, touch and hold the seal in a photo to lift it from the background, then Copy it or tap Add Sticker. It’s designed for people and objects, so it can miss a flat red mark or cut part of the ring away. Check the result closely.
A free background remover in an image editor or online. Keep in mind that an online tool means uploading an image of your personal seal to someone else’s server.
Select the white by colour in an image editor, delete it, and export.

Save as PNG, not JPG. JPG can’t hold transparency and quietly puts the white back. There’s more on that in how to make a transparent signature PNG; it applies to seals exactly the same way.

Then zoom in and check three things. The ring is complete. Thin strokes inside it survived, since some tools keep only the largest shape. It’s still red. Some tools turn everything grey or black, and a hanko should stay the colour of the ink you pressed it with. If it came out pale, a small saturation boost is fine, but don’t repaint it a different red.

4. Place it on the PDF for free with Markup

The built-in Markup tool (open the PDF in Files, tap the pen icon) handles signatures and text well. Seals are more awkward, and it’s better to know that up front:

The Signature tool only accepts a drawing. You can’t import an image there, so it can’t hold your hanko.
On recent iOS versions, Markup’s + menu has an Add Sticker option. If you’ve made a sticker from your hanko in Photos, you can place it on the page and resize it. Whether it appears depends on your iOS version and the app you opened the PDF in, so check your own device rather than assuming it’s there.
What Markup adds is an annotation. It sits on a layer above the page, so until the file is flattened it can be moved or deleted by whoever opens it next, or look different in another viewer.

So finish by flattening. The free Print → Share → Save to Files method in how to flatten a signed PDF on iPhone bakes the seal into the page. Then open the saved copy and zoom in to check the seal is still there and still sharp.

Doing it with Signed

If you sign paperwork with your hanko regularly, the sticker-then-flatten routine gets old. This is a job Signed is built for:

Add your hanko once. In Signatures, open Seals, then scan the seal with the camera or import a photo you’ve already taken. Signed removes the paper but keeps the ink’s own colour, so a red hanko stays red instead of being recoloured like a signature. It also keeps the small strokes that a seal is made of.
Open the PDF from Files, Mail or anywhere you can share a PDF from.
Tap the Seal tool and place your hanko. Pinch to bring it down to the real size and drag it onto the 印 circle or beside your printed name.
Add anything else the form asks for, like the date or your name.
Tap Finish. The PDF you share is flattened, so the seal is part of the page and prints the way it looks on screen.

None of this leaves the phone. Signed doesn’t upload your documents, which is worth having when the file has your name, address and personal seal on it.

Making it look like the real thing

Match the real size. A personal hanko is usually small, often around a centimetre. Hold your physical seal against the screen at 100% zoom if you’re unsure. An oversized seal on a form looks wrong immediately.
Put it where the paper version would go. If there’s a 印 circle, centre the seal on it. If there’s only a printed name, the usual place is on or just to the right of the end of the name. When in doubt, look at a version of the same form you’ve stamped on paper before.
Keep the transparency. The point of placing a seal over the printed name is that the name shows through. If you see a white patch, the background wasn’t removed.
Check the exported file, not just the editor.

Keep the image as safe as the seal

A hanko image is easy to copy. Anyone with the PNG can place it on any document, so treat it like the seal itself. Don’t email the image file around, don’t keep it in a shared or family photo library, and only make a digital copy of a seal that’s yours to use.

Will a digital hanko be accepted?

That’s up to whoever receives the document, and it’s worth being straight about it. An image of your seal on a PDF shows the document was marked with it. It doesn’t prove who placed it, and it isn’t a certificate or a cryptographic digital signature. Plenty of recipients are happy with a stamped PDF. Some will ask for the original stamped paper, and some documents have their own requirements whatever the image looks like. If you’re not sure, ask the sender what they accept before you send it back. The general picture is in are electronic signatures accepted?. Signed is a tool for marking documents, not legal advice.

The short answer

Press a clean impression on white paper using a soft surface underneath, photograph it sharply in daylight with no flash, crop it, remove the white, and save it as a PNG. Place it with Markup’s Add Sticker on recent iOS versions and flatten the PDF afterwards. Or scan it into Signed once, and the Seal tool places it in its own red at the size you choose, in a flattened file.

For a company seal rather than a personal one, see how to add a company stamp to a PDF on iPhone. If your form also needs typed Japanese, there’s a separate guide on filling out a PDF in Chinese, Japanese or Korean on iPhone.