Disclosure. We make Paperlock, a document vault app, and it appears in the table below. Several of the other options are free, already on your phone, and the right answer for many readers. We say which.
The short answer
There's no "lock this file" button in the iPhone's Files app. You can't put Face ID on one PDF in a folder. What iOS can lock on its own:
- A note, in Notes, with Face ID or a password.
- A whole app, with Face ID, by touching and holding its icon (iOS 18 and later).
- Hidden photos: the Hidden and Recently Deleted collections in Photos are locked with Face ID by default.
- A PDF, with its own password, in the Preview app (iOS 26 and later).
Beyond that, you need a password manager that stores files or a vault app. The method to pick depends on one question: are you guarding against someone holding your unlocked phone, or against the file being read somewhere else after you send it? Only a password on the file itself handles the second.
Six ways compared
| What it locks | Protects against | Survives sharing? | Finding it later | Cost | |
|---|---|---|---|---|---|
| Locked notes (Notes) | One note; not notes with PDF or file attachments | Someone holding your unlocked phone | No; what you send is unlocked | Titles stay visible in the notes list | Free |
| Locked or hidden app (Face ID) | A whole app, such as Files or Photos | Someone holding your unlocked phone | No | Content of a locked app is left out of search | Free |
| Hidden album (Photos) | Photos and screenshots of documents | Someone scrolling your camera roll | No | Open Hidden, unlock, scroll | Free |
| Password on the PDF (Preview or our browser tool) | One PDF file | A file sent, uploaded or lost elsewhere | Yes, the password travels with the file | By file name; contents unreadable without the password | Free |
| Password manager with file storage | Files saved inside it | Someone holding your unlocked phone | No; a file you export is ordinary | Search by item name | Free tiers to subscription |
| Vault app (Paperlock) | Every document saved in it | Your unlocked phone, glances at the screen | No; the copy you send is an ordinary file | Ask in plain English | Free for 25 documents; Plus $4.99/month or $39.99/year |
1. Lock a note in Notes
Good for text you'd write down anyway: a policy number, a door code, the details off the back of a card. First choose how notes unlock: Settings → Apps → Notes → Password, then Use Device Passcode (Face ID works with it) or Use Custom Password. Then open the note, tap the menu button at the top, and tap Lock.
Apple lists the limits plainly. You can't lock notes with PDF, file, audio or video attachments, notes with tags, Quick Notes, shared notes or notes that sync with other accounts. The note's title stays visible in the list, so name it "Insurance" rather than "Bank PIN 4471." And if you choose a custom password and forget it, Apple can't recover those notes. If you'd rather keep a note as a file, saving a note as a PDF shows how, and then the PDF methods below apply.
2. Lock or hide the app with Face ID
Touch and hold an app's icon, tap Require Face ID, and the app asks for Face ID or your passcode every time it opens, relocking when you quit it. Apple adds that information inside a locked app doesn't appear in notification previews, search or Siri suggestions. Choose Hide and Require Face ID instead, and the app leaves your Home Screen for a locked Hidden folder at the bottom of App Library. Only apps you downloaded can be hidden; built-in apps like Files and Photos can be locked but not hidden.
This is the quickest fix for the most common problem: you hand your phone to someone to show a photo and they swipe one app too far. It's all-or-nothing, though. Lock Files and every file in it is locked, including the ones you open ten times a day. Our Face ID guide goes into what an app lock does and doesn't stop.
3. Hide photos of documents in Photos
If your passport lives in your camera roll, as most people's does, this one's free and takes five seconds. Select the photo, tap the menu button, tap Hide. Apple says the Hidden and Recently Deleted collections are locked with Face ID, Touch ID or your passcode by default; you'll find Hidden under Utilities in Collections. For one more layer, turn off Show Hidden Album in Settings → Apps → Photos, and it disappears from the app entirely.
The catch is the same as hiding a key under the mat: it's out of view, not organized. Twenty hidden screenshots don't say which is the passport. And the moment you share one, the recipient gets an ordinary photo.
4. Put a password on the PDF itself
This is the only method on this page where the protection goes with the file. Email it, upload it to a landlord's portal, leave it on a shared computer: the PDF still asks for its password.
In Preview (iOS 26 and later), open the PDF, tap the menu next to the file name, tap Lock, type the password twice and confirm. Apple suggests duplicating the file first if you want an unprotected copy. Apple's page doesn't say which encryption Preview uses.
In the browser, our free protect PDF tool runs in Safari on your iPhone. It encrypts the PDF with AES-256 on the phone, nothing is uploaded, and it then reopens its own output to check that your password opens it and that no password doesn't.
Either way, the password is the whole protection. A short phrase of unrelated words beats a clever eight-character one, and there's no recovery if you lose it. Send the password by a different route than the file: a text, a call. Our guides to sharing documents securely from iPhone and sending important documents by email cover the rest.
5. Store files in a password manager
Some password managers keep documents too. In 1Password, for example, you add a Document item and attach the file; their help page suggests receipts for big purchases, photos of your passport and driver's license, and a copy of your will. If you already use one and trust it, this is a sensible home for a handful of key documents. It sits behind the same lock as your passwords, and it works across devices, including non-Apple ones, which nothing else here does as well. If you're part of a family or team, files can go in a shared vault.
Where it's weaker: a password manager is built to find a login, not a document. You name each item yourself, and nothing reads the expiry date off your passport. Our password manager vs. document vault comparison goes through who's better served by which.
6. Use a document vault app
A vault app locks only your documents and leaves the rest of your phone alone. Paperlock is ours. It asks for Face ID or your passcode on open and again after about a minute in the background, and hides its contents in the app switcher. IDs, passports and medical papers show blurred thumbnails until you confirm with Face ID again, so scrolling past them with someone beside you shows nothing. Documents are stored encrypted on the phone.
The difference from a locked folder is finding things. Paperlock reads each document when you add it and files it by itself, so instead of opening "Scan 14.pdf" you ask "when does my passport expire?" and get the answer with the passport attached. Questions need an internet connection and are answered partly on our servers, which process the document only for the request and don't keep it.
Honest limits: iPhone only, no Android or web. No sharing between users, so a family wanting one shared set is better off with a password manager's shared vault. Any document can be exported as a PDF, but the copy you send is an ordinary file; lock it with method 4 first if it matters. For other options in this category, see our private document vault apps comparison.
Which one to use
- One sensitive photo in your camera roll: hide it in Photos. Free, done.
- A few lines of text: a locked note.
- Stopping a friend who's scrolling your phone: lock the app with Face ID.
- A file you're about to send: password-protect the PDF. Nothing else survives the trip.
- Already living in a password manager: keep your key documents there too.
- Dozens of documents you'll need to find later, behind Face ID: a vault.
One rule covers all of them: every Face ID lock falls back to your phone's passcode. If someone knows it, they can open everything except a PDF with its own password. Guard the passcode in public, and the rest of these locks do their job.