Open the PDF on your phone or computer, add your signature with a built-in tool (Markup on iPhone, Preview on Mac) or the free Adobe Acrobat Reader, and save the file. Then upload the signed PDF at sendfaxfast.com, enter the fax number and send it. No printer or scanner needed, unless the recipient requires a handwritten signature.
"Please sign and fax back." It's one of the most common requests that still involves a fax: a lease, a consent form, an authorization, a job offer. You don't need to print anything. Here is how to sign the document on the device you already have and send it back as a fax.
Step 1: Check what kind of signature is accepted
Most offices that say "sign and fax back" simply need to see your signature on the page. But some agencies and forms require a handwritten ("wet ink") signature, or have their own rules for electronic signatures. Check the instructions on the form or letter first. Our guide on faxing documents to Social Security is one example of why this matters.
If a handwritten signature is required, print the page, sign it with a dark pen, and scan it with your phone. See How to fax a document from a phone photo.
Step 2: Sign the PDF on your device
iPhone or iPad
- Open the PDF in the Files app or from your email.
- Tap the Markup button (the pen icon).
- Tap the plus button, choose Add Signature, and sign with your finger.
- Move the signature to the signature line, then tap Done.
Mac
Open the PDF in Preview, click the Markup button, then the Sign button. You can create a signature with your trackpad, or sign on paper and hold it up to the camera. Place it on the page and save.
Windows, Android and Chromebook
The free Adobe Acrobat Reader app (for Windows, Mac, Android and iPhone) has a Fill & Sign tool. Open the PDF, choose Fill & Sign, add your signature, and save a copy. On Windows, the PDF viewer in Microsoft Edge also has a Draw tool that you can use to sign with a mouse, a touchscreen or a pen.
Step 3: Fill in the rest of the form
Forms often need more than a signature: a date, your printed name, initials on every page, or check boxes. Most PDF tools let you add text anywhere on the page. Go through the whole document once before you send it, because a missing initial is a common reason for a form to come back.
Step 4: Check the saved file
- Open the saved PDF again and make sure the signature and all your entries are there.
- Check that all pages are included, in the right order.
- Use dark ink colors. Fax is black and white. Black or dark blue signatures come through best.
Step 5: Fax it back
- Find the fax number. It's usually on the form, in the email, or on the cover sheet the sender used. If the sender gave you their own cover sheet, put it on top.
- Open sendfaxfast.com on your phone or computer and upload the signed PDF.
- Enter the fax number with the country code and your email address.
- Pay for this one fax by card, Apple Pay, Google Pay or PayPal.
- Keep the delivery report from your email with the signed PDF.
Need a cover page? Read What to put on a fax cover sheet or use the free generator.
If you already work with ChatGPT, Claude or Grok, you can also send the signed file from the chat with the SendFaxFast connector and AI fax credits.
What does it cost to fax back a signed form?
| Fax type | Pages | Price (USD) |
|---|---|---|
| Short fax | 1–5 | $2.49 |
| Long fax | 6–20 | $3.49 |
| XL fax | 21–40 | $4.99 |
| XL Fax Plus | 41–100 | from $6.24 |
Prices per fax as of October 2026, the same for the US & Canada (+1), Australia (+61), New Zealand (+64), and 39 more supported countries. XL Fax Plus costs $4.99 plus $1.25 for each started 10 pages beyond 40. Maximum 100 pages per fax. Single faxes need no account and no subscription.
How do I show I sent it?
Keep three things together: the signed PDF, your payment receipt, and the delivery report that confirms the fax was delivered. The report shows when your fax reached the recipient's fax line. It doesn't show who picked it up, so for important deadlines it's worth a short follow-up call. More on this in How do I know my fax went through?
Frequently asked questions
Can I sign a PDF on my phone and fax it?
Yes. On an iPhone, use Markup in the Files app. On Android, use a free app like Adobe Acrobat Reader. Then upload the signed PDF at sendfaxfast.com in your phone's browser.
Is a signature added on screen accepted?
Often, but not always. Some agencies and forms require a handwritten signature. Check the instructions on the form, and ask the recipient if you're not sure.
Do I need a printer to sign and fax back a document?
No, if an on-screen signature is accepted. If a handwritten signature is required, print the page, sign it, and scan it with your phone.
What if the document came as a Word file?
Save or export it as a PDF first, then sign the PDF. PDF keeps the layout intact when it is faxed.
How much does it cost to fax back a signed document?
With sendfaxfast.com, $2.49 for 1–5 pages, $3.49 for 6–20 pages, $4.99 for 21–40 pages, and from $6.24 for 41–100 pages. No account and no subscription.