How to sign a PDF depends on one question: are you the only one who signs, or does someone else have to sign too? To add a signature to a PDF yourself, the tools already on your computer are enough: Preview on a Mac, the free Adobe Acrobat Reader, or your browser. To have a PDF signed by other people and keep a record of who signed when, you need a signing service. This guide covers both, with the steps as the manufacturers describe them.
Sign a PDF yourself
All the methods in this section place an image of your signature on the page. That is enough for a form you send back yourself. It does not record who placed the signature, and anyone who has the file can copy the image or change the text afterwards.
Mac: Preview
Preview comes with macOS. Apple describes the steps in Fill out and sign PDF forms in Preview on Mac:
- Open the PDF in Preview.
- Click the Show Markup Toolbar button (if the Markup toolbar isn't showing), then click the Sign button.
- Create a signature once. You have three choices:
- Trackpad: click Trackpad, sign your name on the trackpad with your finger, press any key, then click Done.
- Camera: click Camera, hold your signature on white paper facing the camera so that it is level with the blue line, and click Done when it appears.
- iPhone or iPad: click Select Device, sign on the device with your finger or Apple Pencil, then tap Done.
- Click the signature you want to add, drag it to where it belongs, and use the handles to adjust the size.
- Save the file.
Preview keeps the signature, so the next time you only pick it from the list.
Windows and Mac: Adobe Acrobat Reader
Acrobat Reader is free. Adobe's help page Sign PDFs lists these steps:
- Open the PDF you want to sign.
- Click the Sign icon in the toolbar, or choose Tools > Fill & Sign.
- Choose whether you want to add your signature or just your initials.
- The first time, create the signature: type your name, draw it, or select an image of your signature.
- Click Apply, then click the place in the PDF where the signature belongs.
- Save the file.
In the browser: Chrome, Edge, Firefox
Your browser can also add a signature to a PDF, without an extra program.
- Chrome: Google's help page Manage PDFs in Chrome describes how to draw a signature: select Draw, then Pen on the right panel, choose size and colour, and download the file with your changes.
- Edge: Microsoft's documentation of the Edge PDF reader names inking on PDF files for signing and filling out forms.
- Firefox: Mozilla's PDF editor page says: click the signature icon, then "Add new signature", choose Type, Draw or Image, and click Add.
With a mouse, a drawn signature often looks shaky. A typed signature or a photo of your signature on paper usually looks cleaner. If you need a clean image of your signature first, the signature generator creates one as a PNG.
Have a PDF signed by others
Once a second person has to sign, emailing a file back and forth gets messy: who has the current version, did anyone change something in between, and when exactly did each person sign? This is the case canusign is built for.
- Upload your PDF.
- Place a signature field for each person, plus initials or a date if needed.
- Send each person their link, or share one link. Signers need no account.
- When everyone has signed, you download the signed PDF.
What the signed file contains:
- An audit certificate at the end: who signed when, the document ID and a QR code.
- A timestamp from DigiCert under RFC 3161, which Adobe Acrobat shows in the signature properties.
- The document ID on every page, so a printout can be traced back too.
- A verification page: anyone who receives the PDF can check on canusign.com/en/verify that it matches the version stored with us. The file stays in the browser.
You pay per document, without a subscription; the current prices are on the pricing page. canusign creates a simple electronic signature. It is valid where the law does not require a handwritten signature or notarisation.
Which method fits
| Situation | Method |
|---|---|
| You fill in and sign a form yourself | Preview, Acrobat Reader or the browser |
| You only need an image of your signature | Signature generator |
| Someone else has to sign, or several people | canusign |
| You need to prove later that the file is unchanged | canusign, with the verification page |
Is a signature added to a PDF legally binding?
In the United States, the ESIGN Act says that a signature or contract "may not be denied legal effect, validity, or enforceability solely because it is in electronic form" (15 U.S.C. § 7001). In the EU, the eIDAS regulation says the same for electronic signatures. Both laws have exceptions, for example wills. Our article digital vs wet signature lists them.
Whether a signature is valid and whether you can prove it are two different questions. An image in a PDF can be valid, but if the other side disputes it, you have nothing besides the image. A record of who signed when, and a way to show the file has not changed, is what helps in that case.
FAQ
How do I sign a PDF for free?
On a Mac with Preview, on Windows and Mac with Adobe Acrobat Reader, or in Chrome, Edge or Firefox. All of them are free and add your signature as an image.
How do I add a signature to a PDF on Windows?
Install Adobe Acrobat Reader, open the PDF, click the Sign icon and follow the steps above. Without installing anything, use Edge, Chrome or Firefox.
Can someone check later whether a signed PDF was changed?
For a PDF signed with canusign, yes: on the verification page, by document ID or by dropping the file. How to check other PDFs, and what that can and cannot prove, is in the guide Check a PDF for changes.