To sign a PDF for free, open it in Adobe Acrobat Reader, choose Fill & Sign, type, draw or import your signature, then place it and save. On a Mac, Preview does the same without extra software, and on an iPhone or iPad you use the signature tool in the Files app or Markup. On Android you can use the free Acrobat Reader app or write on the PDF in the Google Drive app. All of these add an electronic signature, and none of them adds a certificate-based digital signature, which is a different thing and is covered further down.
Step 1: Open the PDF in Adobe Acrobat Reader
Adobe Acrobat Reader is free desktop software for Windows and Mac, and Adobe lists signing among the things you can do with it at no cost. Open the PDF document or form you want to sign. Adobe is rolling out a new layout in which the tools appear on the left side of the screen, so the names below can differ slightly between versions.
Step 2: Open the Fill & Sign tool
In the classic layout, click the Sign icon in the toolbar, choose Tools > Fill & Sign, or choose Fill & Sign in the right pane, then click Fill and Sign. In the new layout, select All tools > Fill & Sign. Form fields are detected automatically. Hover over a field until a blue box appears, click inside it and type to fill it in. On a PDF without form fields, you can still click where you want to add text.
Step 3: Create your signature
Click the Sign icon in the toolbar and choose whether you want to add your signature or only your initials. If you have signed before, your saved signature appears as an option. If you are signing for the first time, the Signature panel opens with three ways to create one.
Type: type your name and click Change Style to pick a different signature style
Draw: draw your signature in the field with a mouse, a trackpad or a touch screen
Image: browse to a picture of your handwritten signature. Acrobat accepts JPG, JPEG, PNG, GIF, TIFF, TIF and BMP files
Save Signature: when this box is ticked and you are signed in, Adobe stores the signature in Adobe Document Cloud so you can reuse it
Step 4: Place the signature on the page
Click Apply, then click the place in the PDF where the signature or initials should go. To move it, click the field to highlight it and use the arrow keys. To resize or delete it, use the options in the field toolbar. In the new layout, you can also drag a signature or initials from the E-sign panel into a field.
Step 5: Save the signed PDF
Save the document. Adobe explains that the signature and any text you added become part of the PDF when you save it. Keep an unsigned copy if you might need to change the content later. Adobe notes that in Acrobat on mobile the PDF flattens on save and cannot be unsigned, and that in Acrobat on the web a saved signature cannot be edited again. Then send the signed file back the way the sender asked, usually by email.
How do I sign a PDF on a Mac?
Use Preview, the PDF viewer built into macOS. Open the PDF in Preview. If the Markup toolbar is not showing, click the Show Markup Toolbar button, then click the Sign button. The first time, create a signature in one of the three ways below. Then click the signature to add it to the PDF, drag it where you want it and use the handles to adjust its size. If you use iCloud Drive, your signatures are also available on your other Macs that have iCloud Drive turned on. To delete a saved signature, click the Sign button, hold the pointer over the signature and click the X to its right. Apple notes that this removes it from all apps that use Markup on your Mac.
Trackpad: click Trackpad, click the text as prompted, sign with your finger on the trackpad, press any key and click Done. On a Force Touch trackpad, pressing harder gives a darker line
Camera: click Camera and hold your signature, on white paper, facing the camera so it is level with the blue line, then click Done
iPhone or iPad: click Select Device, sign on the device with your finger or an Apple Pencil (iPad) and tap Done. The devices must meet Apple's Continuity requirements
Replying to an email: open the PDF attachment from Mail in Preview, sign it, choose File > Save and select Reply to the sender or New Mail Message
How do I sign a PDF on an iPhone or iPad?
Open the PDF on your iPhone or iPad. If prompted, open it in the Files app and tap Save. Tap the Add button, tap Add Signature, sign your name with your finger (or an Apple Pencil on iPad) and tap Done. Drag the signature to where it should appear on the page. When you are finished, tap the Menu button and tap Export, Print or the Share button to send the signed document, or tap the Back button to save it. In apps that support Markup, such as Notes and Photos, tap the Markup button, tap the Add button and tap Add Signature. Your device saves the signature for next time, and you can create several, for example your full name and your initials. To start a signature again while drawing it, tap Clear.
Rotate your iPhone for more room to sign, as Apple suggests
Move the signature by dragging it, and resize it with any blue dot on its frame
Acrobat Reader app: open the PDF, select Fill & Sign in the bottom menu, then Signature > Add signature. Draw it, use an image or capture one, tap Done and tap where it should go
How do I sign a PDF on Android, on Windows or in a browser for free?
On Android, Google documents freehand writing on PDFs in two of its own apps, and Adobe's free app has a full signature tool. On Windows, Adobe Acrobat Reader (the steps above) is the most complete free option. In a browser, you can use Adobe's free online tool or the PDF reader built into Microsoft Edge.
Acrobat Reader for Android: open the PDF, select Fill & Sign in the bottom menu, then Signature > Add signature. Draw it, use an image or capture one, tap Done and tap where it should go
Google Drive app (Android 6.0 or later): open the PDF, tap the annotate button at the bottom right, pick the pen and write your signature with a finger or stylus. Save the original or a copy with a new name
Files by Google: open the PDF, tap Edit at the bottom right, choose the Pen and sign, then tap Save copy at the top right. The signed copy is uploaded to your Google Drive and the original on your phone stays unmarked
Adobe Acrobat online: at adobe.com, select a file, add your signature with the tools in the Sign panel and click Next, then download the file or get a link. Adobe says the tool is free, but you must be signed in to an Adobe account to complete it
Microsoft Edge: Microsoft says the built-in PDF reader on Windows and macOS lets you draw on a PDF with ink, which it describes as handy for signing or filling out forms. Select Save in the toolbar when you are done
What is the difference between an electronic signature and a digital signature on a PDF?
Adobe draws the line clearly. An electronic signature is any electronic mark that shows a person's intent to sign, such as a typed name, a drawn signature or an uploaded image of handwriting. Everything in the steps above is an electronic signature. A digital signature is a specific kind of electronic signature that uses a certificate-based digital ID to verify the signer's identity and to detect changes made after signing. The digital ID contains a private key for signing and a certificate for checking the signature. In Adobe Acrobat on the desktop, you add one with All tools > Use a certificate > Digitally sign. Draw a rectangle where the signature should appear, choose your digital ID in the Sign with a Digital ID dialog box (or create one with Configure New Digital ID), check the details, enter your digital ID password, select Sign and save the file.
Lock document after signing: blocks all further edits and extra signatures, so leave it unticked if other people still need to sign
A PDF signed with a digital ID becomes read-only for others
The Adobe Approved Trust List is Adobe's programme for digital IDs whose signatures are trusted when the document is opened in Acrobat or Reader
Is a signed PDF legally binding?
In most business situations an electronic signature on a PDF can be binding, as long as the person meant to sign. What varies is the proof you have, and whether a specific law requires a stricter form. A signature image pasted into a PDF is easy to copy to another document, so on its own it proves little about who placed it. A signature collected through an e-signature service with an audit trail, or a certificate-based digital signature, gives much stronger evidence. This is general information, not legal advice.
EU: under article 25 of the eIDAS Regulation (EU) No 910/2014, an electronic signature cannot be denied legal effect or admissibility as evidence solely because it is electronic or not qualified. Only a qualified electronic signature has the equivalent legal effect of a handwritten signature
UK: section 7 of the Electronic Communications Act 2000 makes an electronic signature admissible in evidence on the authenticity and integrity of the data it is attached to
US: the ESIGN Act (15 U.S.C. 7001) says a signature or contract may not be denied legal effect, validity or enforceability solely because it is in electronic form. Under section 7 of the Uniform Electronic Transactions Act, enacted by the states, an electronic signature satisfies a law that requires a signature
Germany: when the written form required by law is replaced by the electronic form, § 126a BGB requires the signer's name and a qualified electronic signature
Netherlands: article 3:15a of the Dutch Civil Code gives an advanced or other electronic signature the same legal effect as a handwritten one if the signing method is sufficiently reliable for its purpose and the circumstances
Why won't a PDF let me sign it?
Most signing problems have a known cause. These are the ones Adobe, Google and Microsoft describe.
The PDF has no form fields: Fill & Sign in Acrobat still lets you add text and a signature to these flat forms. Turning a flat form into a fillable form needs the Prepare a form tool in Acrobat Pro, which Adobe says is not available in Acrobat Reader
The PDF is already signed with a digital ID: it has become read-only. If you were the only signer, right-click your signature and select Clear Signature. Otherwise, ask the sender for an unsigned copy
Someone ticked Lock document after signing: the file is locked for everyone. Adobe says the only solution is to recreate the PDF or request an unsigned copy from its owner
Acrobat asks for a digital ID you do not have: select Configure New Digital ID, or use an ordinary electronic signature if a certificate is not required
The form will not fill in Microsoft Edge: Microsoft says Edge does not support XFA, a legacy form format. Open the file in Acrobat Reader instead
The Form Filling option is missing in the Google Drive app: Google says you may not be able to fill out that PDF in Drive
How do you get a quote or proposal signed without printing it?
Many quotes still travel as PDFs. You export the quote, email it, and the client signs it in one of the ways above and sends it back. That works, but you depend on the client to sign, save and return the right file, and a pasted signature image is weak proof if the deal is ever disputed. Adobe says Acrobat Reader includes a limited number of signature requests through Fill & Sign without a subscription, and that signers need no Acrobat subscription to sign. Google Workspace eSignature can also send a PDF from Google Drive for signing on eligible plans. Proposal Expert takes a different route: you create the quote or proposal in the app, send it and track it, and the client signs online with an eIDAS simple electronic signature, a trusted timestamp and a sealed audit trail. Proposal Expert's free plan includes 3 proposals and 3 electronic signatures a month. It does not sign PDFs you upload, only proposals created in the app.
Frequently asked questions
How do I sign a PDF for free?
Use Adobe Acrobat Reader, which is free on Windows and Mac: open the PDF, open Fill & Sign, add your signature and save. On a Mac you can also use Preview, on an iPhone or iPad the Files app or Markup, and on Android the free Acrobat Reader app or the annotate tool in the Google Drive app. In a browser, Adobe's online sign tool is free with an Adobe account.
Can a PDF file be signed electronically?
Yes. Typing, drawing or placing an image of your signature in a PDF creates an electronic signature. Under the US ESIGN Act and article 25 of the EU eIDAS Regulation, a signature cannot be denied legal effect just because it is electronic. For stronger proof of identity, you can add a certificate-based digital signature in Adobe Acrobat.
How can I add a handwritten signature to a PDF document?
Photograph or scan your signature and import it with the Image option in the Fill & Sign tool of Acrobat Reader. Adobe advises signing in black ink in the middle of a clean sheet of white paper and lighting the page so no shadows fall across the signature. You do not need to crop the image, because Acrobat imports just the signature if the photo or scan is fairly clean. On a Mac, Preview can capture your signature with the built-in camera.
How do I ask someone else to sign a PDF?
Acrobat Reader lets you request a limited number of signatures through Fill & Sign without a subscription, and signers can sign in a web browser or on a mobile device without an Acrobat subscription. With an eligible Google Workspace plan, you can open the PDF in Google Drive and click Menu > eSignature to add signature fields and send the request.
Can I remove or change my signature after saving the PDF?
Often not. Adobe says that in Acrobat on mobile the PDF flattens on save and cannot be unsigned, and that in Acrobat on the web a saved signature cannot be edited. With a digital ID signature, you can clear your own signature if you were the only signer. Otherwise, go back to an unsigned copy, which is why it pays to keep one before you sign.