A lease, a school permission slip, an HR form: someone sends you a PDF and asks you to sign it and send it back today. The old routine is print, sign, scan, email. You can skip all of that. Every common device can sign a PDF for free, and for everyday paperwork a signature added on screen is accepted the same way as a scanned one.
This guide gives the free route for each device, the steps in a browser tool that works on all of them, and one practical finding from our own tests: how to turn a photo of the signature you write on paper into a clean signature, and why the usual "remove white" trick leaves grey smudges.
The free way on each device
| Your device | Free way to sign | How |
|---|---|---|
| Any device with a browser | Sign PDF on this site | Steps below. Nothing to install, no account, the file stays on your device |
| Mac | Preview, built in | Markup toolbar → Sign; sign on the trackpad or hold paper up to the camera (Apple Support) |
| iPhone or iPad | Markup, in Files and Mail | Open the PDF, tap Markup, then + → Add Signature and sign with your finger (Apple Support) |
| Windows | Adobe Acrobat Reader (free download) | Open the PDF and use the Fill & Sign tool or the Sign icon in the toolbar (Adobe Help) |
| Android | Adobe Acrobat Reader app (free) | Open the PDF in the app and use its Fill & Sign tool (Adobe Help) |
The device routes are free, but each keeps you in one app: Preview's signature syncs through iCloud, and Acrobat saves your signature only when you sign in to an Adobe account, and limits how many signature requests you can send to other people for free. If you just need to sign one file and send it back, a browser tool is often quicker, and it works the same on a borrowed laptop, a work computer where you cannot install anything, or a phone.
Sign a PDF in your browser, step by step
- Open Sign PDF and drop the PDF on the box, or tap it to choose the file.
- Click Create signature and make it one of three ways: draw it with a mouse, finger or stylus; type your name and pick a handwriting style; or use a photo of your real signature (more on that below).
- Click Place on page. Drag the signature onto the line and pull the round corner handle to resize it.
- Add the date and your printed name the same way, with Add date and Add text.
- Documents that need initials on every page: select the initials and click Copy to every page. Each copy lands in the same spot, even when pages differ in size.
- Click Save signed PDF and download it. The file name ends in
-signed.pdf; the original is not changed.
If the PDF has boxes to type into (name, address, tick boxes), fill those first with Fill PDF Form, then click Sign it under the result to carry the filled form straight into the signing tool. If you cannot type into the boxes at all, the form is just a picture of a form; place text with Add text in Sign PDF instead.
Using a photo of your real signature
Drawing with a mouse rarely looks like your signature. The best-looking result comes from the one you already write: sign a sheet of white paper with a dark pen, take a photo, and let the tool keep the ink and drop the paper. The catch is the photo. Rooms have shadows and warm lamps, and a phone held over the page often casts its own shadow.
We tested how two ways of removing the paper cope with that. We made signature photos with a known answer — the exact ink pixels are known — under four kinds of light, with a dark gel pen and a lighter blue ballpoint. Then we counted how much of the paper each method wrongly kept as "ink":
| Light in the photo | "Remove white" at the usual setting | Sign PDF's photo clean-up |
|---|---|---|
| Even daylight | 0% of the paper left | 0% |
| Shadow across one corner | 39% of the paper left as grey | 0% |
| Phone's shadow over part of the page | 27% | 0% |
| Warm lamp from one side | 50% | 0% |
Both methods kept 100% of the ink in every photo. The difference is the paper. The simple method treats everything darker than near-white as ink, so a shadowed corner or yellow lamp light turns into a grey patch around your signature — the tell-tale box you sometimes see on signed documents. It can be tuned by hand: a much stricter setting cleaned most of our photos, but the best value was different for the gel pen and the ballpoint, and at the halfway setting a shadowed corner still left 2% of the paper behind. Sign PDF instead estimates the colour of the paper around every part of the photo, so it needs no tuning and left no paper in any of the eight photos.
What helps whichever tool you use:
- Sign large, across most of the width of the paper. It is scaled down on the page, so a big signature stays sharp.
- Use a dark pen on plain white paper, not lined or squared paper.
- Shoot from directly above, filling the screen with the signature, near a window in daylight. Turn the flash off: it adds a bright spot.
- If specks of paper remain, move the clean-up slider up; if thin strokes vanish, move it down.
Prefer a signature file you can reuse elsewhere, such as in an email footer or a Word document? The signature generator makes the same three kinds of signature as a transparent PNG or SVG.
Before you send it
- Check what kind of signature is asked for. A picture of your signature on the page is an electronic signature, and US and EU law accept electronic signatures for most everyday agreements. Some documents ask for a certificate-based digital signature instead — certain bank, government and court forms. What a placed signature proves and what it does not is explained in what is inside a signed PDF.
- Look at the file size. A scanned contract can be too large for an upload form or an email before you even sign it. Compress PDF shrinks scans the most.
- Personal details? If the document contains an ID number or bank details and goes by email, you can add a password and send the password by text message.
- Keep a copy of the signed file and of the email you sent it with. For an agreement between two people, that is your record of when and to whom you sent it.
How we tested
The photo test used synthetic photos so that the right answer was known for every pixel: the same signature strokes drawn on off-white paper at 1600 × 700 pixels, under even light, a 55% darker corner, a soft phone-shaped shadow, and a warm light fading across the page, with a dark gel ink and a lighter blue ballpoint ink and a little camera noise. "Remove white at the usual setting" keeps every pixel darker than 200 on a 0–255 brightness scale, the tolerance many background removers start with; the stricter settings we tried ranged from 60 to 240. Sign PDF's result came from the site's own photo clean-up code at its default strength. Tested on 29 September 2026.