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Add a signature to a PDF

Adding a signature to a PDF means putting a picture of your handwriting on the page. A free reader does it in a minute, and the quality of the result depends almost entirely on how you captured the handwriting. This guide covers both, plus what to do with the file once the signature is on it.

Add signature to PDF

Three ways to get your signature onto the page

You can draw it live with a trackpad, a finger or a stylus. You can photograph a signature written on paper and let the reader lift it off the white background. Or you can type your name in a script typeface, which some readers offer and nobody is really fooled by.

The photographed version wins. Real handwriting has pressure and speed in it that no trackpad reproduces, and the capture takes about thirty seconds with a pen, a white sheet and a phone camera.

Making a clean signature image

Sign a blank white sheet with a black pen, thicker than you would normally use. Photograph it straight on in daylight, without a shadow across the page. If your reader accepts an image file rather than a live capture, crop it tight to the ink first.

Transparency matters if you are placing the image yourself rather than using the reader's signature feature. A PNG keeps a transparent background, so the signature sits on the page instead of arriving inside a white rectangle that covers the line underneath it.

Placing it in a free reader

Preview on macOS, Markup on iOS and Acrobat Reader on Windows all store the signature after the first capture, so every document after that is drag, size, save. Put the box on the signature line rather than near it, and keep the height close to the surrounding text.

Nothing about this uploads the document if you use software already on your machine. That is worth caring about, because contracts are exactly the class of file people hand to a random website without thinking.

If the PDF has a signature field

Some documents ship with a real form field waiting for a signature. Clicking it in a reader starts the certificate route, not the drawing route, and it will ask for an identity rather than a picture.

Fields like that do not survive the tools here. Merging or reordering a document copies its pages and leaves the form structure behind, and the merge tool says so before it runs by naming which of your files carry interactive form or signature fields.

Adding a signed page back into the contract

A common version of this job is a single page that came back signed on paper. Photograph it, turn it into a page with Images to PDF at A4 or Letter so it matches the rest, then merge it in and drop the unsigned original.

Organize pages handles the swap by thumbnail, so you can see the signed sheet sitting in the right slot. Both steps compare the output against the input page by page before offering a download.

The file got bigger

A photographed signature is a photograph, and a phone camera produces a large one. Dropping a full resolution image into a text document can multiply its size, which is why the signed copy suddenly bounces off a mailbox.

The compress tool takes a target size and works down to it in this tab. It reads the result back and checks the text is still selectable before you get the file, so the contract does not come back as a picture of itself.

What the recipient sees

A drawing on a page, which is what a scanned signature has always been. It carries no proof of who drew it, and anyone who receives the file can lift the image out and reuse it. That is a property of every scanned signature ever posted.

If the document is worth more than that, read the comparison guide, and the signing guide covers the per-platform steps in more detail.

Questions people ask

How do I add a handwritten signature to a PDF for free?
Use software you already have. Preview on macOS, Markup on iOS and the free Acrobat Reader on Windows all capture a signature once and then place it on any document with a drag.
What is the best way to get a clean signature image?
Sign a white sheet with a thick black pen and photograph it straight on in daylight. A camera capture keeps the pressure and speed of real handwriting, which a trackpad drawing never manages.
Can I add a signature to a PDF on my phone?
Yes. Markup is built into the Files app and into Mail on iOS, so an attachment can be signed where it landed. A stylus gives a better line than a finger.
Why is my PDF so large after I added a signature?
The signature is a full resolution photograph sitting on the page. Run the file through the compress tool with a size target and it comes back smaller with the text still selectable.

Do it now

The tool runs in this browser. Your file never leaves the machine, and the result is checked before you download it.

Add signature to PDF

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