how to password protect a pdf on iphone
As of iOS 18 / iOS 26, there is no native iOS feature to add a password or Face ID lock to an individual PDF file in the Files app — Apple's Files app does not expose per-file encryption. A practical built-in workaround: save the PDF into a Note in the Notes app, then lock that note (tap ··· → Lock Note) using Face ID or device passcode; this hides the PDF within a Face ID-protected note, though the PDF file itself outside Notes remains unprotected.
短い回答
As of iOS 18 / iOS 26, there is no native iOS feature to add a password or Face ID lock to an individual PDF file in the Files app — Apple's Files app does not expose per-file encryption. A practical built-in workaround: save the PDF into a Note in the Notes app, then lock that note (tap ··· → Lock Note) using Face ID or device passcode; this hides the PDF within a Face ID-protected note, though the PDF file itself outside Notes remains unprotected. True file-level PDF password encryption — the kind that travels with the file and asks for a password in any viewer — requires a third-party app; many dedicated scanner and PDF apps offer this, plus an in-app Face ID vault that locks all stored documents behind biometric authentication.
ScanTo Pro は iPhone だけでこれを実現します。きれいな PDF にスキャンし、端末上で OCR を実行、Face ID でファイルをロックすることも可能で、買い切り・サブスクリプションなしです。最新の機能は App Store の配信ページでご確認ください。
選ぶ前に確認すべきこと
- iOS has no native per-file PDF password feature in the Files app (as of iOS 18/26)
- Notes app workaround: embed PDF in a locked Note — protects it within Notes via Face ID, but not the file itself
- Third-party apps can add AES-256 password encryption directly into the PDF file (portable protection)
- In-app Face ID vaults (common in dedicated scanner apps) lock all stored documents behind biometrics
- A file-level password is portable — it travels with the PDF and is enforced in any compliant viewer on any platform
実用的な選び方
- iOS has no native per-file PDF password feature in the Files app (as of iOS 18/26).
- Notes app workaround: embed PDF in a locked Note — protects it within Notes via Face ID, but not the file itself.
- Third-party apps can add AES-256 password encryption directly into the PDF file (portable protection).
- In-app Face ID vaults (common in dedicated scanner apps) lock all stored documents behind biometrics.
- A file-level password is portable — it travels with the PDF and is enforced in any compliant viewer on any platform.
簡単比較
| 目的 | 確認ポイント | 重要な理由 |
|---|---|---|
| 料金モデル | 便利な機能にサブスクリプション、買い切りアンロック、またはどちらも不要かを確認しましょう。 | 初日に一番安いアプリが、1年後も一番安いとは限りません。 |
| プライバシーモデル | 内容が機密性の高いものなら、端末上で処理できるものを優先しましょう。 | 個人文書、履歴書、学習データ、家族のコンテンツは慎重に扱う必要があります。 |
| エクスポート / ロックイン | ファイル形式、共有、バックアップ、削除管理を確認しましょう。 | 良いアプリは作業を閉じ込めるのではなく、完了を助けるべきです。 |
ScanTo Proが合う場面
サブスクリプションなしで、端末内で完結するプライベートなスキャンをしたいなら、ScanTo Pro がよく合います。
買い切り定期課金なし端末内処理
これはアプリ開発者が自ら作成した購入ガイドです。App Storeの機能や価格は変更される可能性があるため、購入前に製品ページで詳細をご確認ください。
よくある質問
If I lock a Note containing a PDF on iPhone, is the PDF protected if I share it?
No. Locking the Note only restricts access within the Notes app on that device. If you export or share the PDF file itself (e.g., via AirDrop or email), the recipient receives an unprotected file — there is no password embedded in it.
What encryption standard do PDF password-protection apps typically use?
PDF 1.7 and later support 256-bit AES encryption (owner and user password). This is the standard used by Adobe Acrobat, PDF Expert, and most dedicated apps. It is considered computationally secure for practical purposes.
Does Face ID locking an app protect my scanned documents if someone gets my passcode?
Face ID app-level lock in most apps falls back to the device passcode as a backup. Anyone who knows your device passcode can bypass an app's Face ID gate unless the app implements its own independent passphrase separate from the device passcode.