How to password protect a PDF on iPhone
iOS has no built-in command for encrypting a PDF - the Files app creates PDFs but cannot lock them, and Preview's password option only exists on a Mac. On a phone, you set the password while the PDF is being built, so no unprotected copy ever exists. Here is how PDF passwords work, and how to send one safely.
The short answer
Set the password while the PDF is being created. iOS itself has no "add a password to this PDF" command - the Files app can create PDFs but not encrypt them, and Preview's password option is a Mac feature. On a phone, the practical route is a converter that offers password protection as part of building the file, so the PDF is encrypted from the moment it exists.
What a PDF password actually does
A PDF can carry two different kinds of password, and they protect very different things:
- An open password (a user password) encrypts the document's contents. Without it, the file will not open at all - not in Preview, not in Acrobat, not in a browser. This is the one that matters when you are sending something private.
- A permissions password (an owner password) lets the file open freely but marks it as not-to-be-printed or not-to-be-copied. Whether that is honoured is entirely up to the software opening it, and plenty of software ignores it. Treat it as a request, not a lock.
What a password does not do is hide the file's existence, stop someone forwarding the whole encrypted file, or help at all if you send the password in the next message on the same channel.
When it is worth doing
Any document you would not want read by whoever else has access to the recipient's inbox, or by anyone who picks up an unlocked phone the file was AirDropped to:
- Payslips, tax paperwork, bank letters and statements
- Passport, driving licence and ID scans
- Signed contracts, tenancy agreements, anything with your signature on it
- Medical letters and test results
- Anything with a full address, a date of birth and an account number on the same page - the three things that together make identity fraud straightforward
How to add a password on iPhone
In JPG To PDF Converter PRO, the password is part of the page setup rather than a separate step afterwards:
- Tap JPG to PDF and select the photos or scans that make up the document.
- Open the settings and set the page size, orientation and quality as usual.
- Turn on password protection and enter the password you want.
- Preview the document, then save or share it. The file that leaves your phone is already encrypted - there is no unprotected copy sitting in Files waiting to be cleaned up.
Choosing a password that is worth setting
An encrypted PDF is exactly as strong as the password on it, and PDF passwords get guessed by software that tries millions of candidates per second.
- Length beats complexity. Four unrelated words are both easier to say over the
phone and harder to crack than
P@ssw0rd!. - Never reuse an account password. You are about to send this one to someone else, possibly in writing.
- Avoid the obvious. A date of birth, a surname, or a number that appears on the document itself is the first thing anyone tries.
- Do not put it in the file name.
Payslip-pw-1234.pdfdefeats the purpose.
Sending the password
This is where most of the security is won or lost. A password in the same e-mail as the attachment protects against nothing: whoever reads the e-mail has both halves.
- Use a different channel. File by e-mail, password by phone call or text message.
- Better still, say it out loud. Nothing written down, nothing to find later.
- Agree it in advance for regular exchanges. If you send your accountant something every month, settle the password once rather than transmitting a new one each time.
Before you send it
- Open the file yourself. Tap it in Files and confirm you are actually asked for a password, and that the one you set works.
- Check every page opened. Encryption applies to the whole document, but it is worth confirming the document is the one you meant to send.
- Tell the recipient it is locked. Otherwise they assume the file is broken.
Common mistakes
- Sending the password with the file. The most common mistake and the one that undoes everything else.
- Assuming a permissions password stops copying. It is a flag some readers respect and others ignore. Only an open password encrypts anything.
- Leaving the unprotected original in Files. If you made an unlocked version first, delete it - and empty Recently Deleted.
- Forgetting the password. There is no recovery. A properly encrypted PDF with a lost password is gone; keep it in your password manager.
- Password-protecting it on a website. To add the password, the site needs the unencrypted document on its server first. You have handed over exactly the thing you were protecting.