How to Password Protect a PDF on iPhone
Updated
Quick answer
Open the PDF in PDF Slayer, choose Password Protect, set a password, and optionally restrict permissions like printing or copying. Save, and the file is AES-encrypted on your device — it stays locked wherever you send it.
Sending a contract, payslip, or anything with personal data over email or chat? The attachment can be forwarded, synced, and backed up in places you will never see. A password on the PDF means only someone with the password can open it, wherever the file ends up.
There is an irony in using an online tool to "secure" a PDF — you upload the unprotected document to someone else’s server first. Encrypting on-device closes that gap: the file is never exposed at any point.
Password-protect a PDF with PDF Slayer
Open the PDF
Launch PDF Slayer and open the document you want to lock.
Choose Password Protect
Open the protection tool.
Set a strong password
Pick a password you can share with the recipient through a different channel (tell them in person or by phone — not in the same email as the file).
Set permissions
Optionally restrict printing or copying for extra control over how the document is used.
Save the encrypted copy
Save. The PDF is now AES-encrypted and stays protected wherever it travels.
Free on the App Store. Works 100% offline — your documents never leave your iPhone.
Get PDF Slayer FreeWhat the password actually protects
PDF password protection encrypts the file’s contents with AES. Without the password, the document cannot be opened — not by an email provider scanning attachments, not by someone who finds it in a shared folder years later.
Two practical rules: use a password that is not guessable from context (not the recipient’s name or "invoice2026"), and never send the password in the same message as the file.
Need to remove a password later?
If you receive protected files — bank statements are the classic case — and want to store them unlocked in your own secure archive, PDF Slayer can also remove protection when you know the current password. See the unlock guide below.
Frequently asked questions
What encryption does PDF Slayer use?
AES encryption — the standard for PDF protection — with optional permission controls for printing and copying.
Does the password stay when I email the PDF?
Yes. The encryption is part of the file itself, so it stays locked no matter how it is shared or stored.
What if I forget the password?
There is no backdoor — that is the point of encryption. Keep the password somewhere safe, like a password manager.
Is my PDF uploaded to add the password?
No. Encryption happens entirely on your iPhone, so the unprotected file is never exposed to any server.