How to sign a PDF on your iPhone or Android phone

No app, no account, no upload

Cachety runs in your phone's browser, such as Safari or Chrome. There is nothing to download from an app store and no account to create. The document is processed on the phone itself and never uploaded: the page is technically forbidden from contacting any other website.

Step by step

1. 1Save the PDF you received to your phone. In most email apps, tap the attachment, then save it to Files on iPhone or to Downloads on Android.
2. 2Open cachety.com/en/sign in your browser, tap the drop area and choose the PDF. A photo of a paper document works too.
3. 3Draw your signature in the box with your finger. Not happy with it? Tap Undo last stroke, or Clear, and try again. You can also type your name instead, or upload a photo of your signature.
4. 4Choose what goes under the signature, if anything. Today's date is on by default, and you can add the place and a note such as ‘Read and approved’.
5. 5Go to Place, check, download. Your signature appears at the bottom right of the last page. Drag it with your finger and use the corner to resize it.
6. 6Check the preview, download the signed PDF, then send it back by email or messaging app.

Write a little larger than you would on paper, and take your time. The empty space around your signature is trimmed automatically, so it stays sharp once it is placed on the page.

Prefer a photo of your signature?

If signing with your finger feels awkward, sign a sheet of white paper with a dark pen, take a photo of it in daylight, and choose Upload. The white background is removed for you. If some of the paper still shows, move the Sensitivity slider. iPhone photos (HEIC) work too.

Check that it stays on your phone

Once the page has loaded, switch on aeroplane mode, then choose your PDF and sign it. Everything keeps working, which shows that nothing is sent anywhere. Your signature is not saved: close the tab and it is gone.

Options before you download

• ‘Also initial every page’ adds a small copy of your signature to the other pages.
• ‘Make it smaller’ keeps the file under the size an email or a website allows.
• ‘Lock with a password’ is off by default, so the recipient can open the file straight away.
• After the download, a fingerprint of the file is shown. Keep it and send it with the document: if a different version ever turns up, its fingerprint will not match, so you can tell it is not the file you sent.

What this signature is worth

A signature drawn on your phone and placed on the document is what is commonly called a simple electronic signature. It is usually accepted for everyday documents, such as school and club forms, consent forms, quotes and rental paperwork. If it is ever disputed, whoever relies on the document must prove who signed it: keep the email or message it was sent with.

It is not the right tool when a qualified signature with a certificate is required, for a will or a deed, or when the other party insists on its own signing platform (some loan or insurance contracts, some official procedures). And as with a scanned paper signature, someone could cut your signature out of the copy and reuse it. Adding a watermark with the purpose and the recipient, and initialling every page, limits that risk. This is not legal advice.