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PDF加密/解密
為PDF設定密碼保護或移除密碼保護
拖曳PDF檔案到此處，或點擊選擇
最大檔案大小：128 MB
所有處理均在瀏覽器本地完成，檔案不會上傳到伺服器。
用密碼加密 PDF — 瀏覽器端 AES-256 保護
Add password protection to any PDF using AES-256 encryption, the strongest commercially-available PDF encryption. Your PDF stays in your browser during the encryption process — only the encrypted result leaves your device when you save. No upload, no sign-up, no daily limits.
100% FreeNo UploadNo Sign-upAES-256 Encryption
使用步驟
- Drop Your PDF: Drag any PDF in. Already-encrypted PDFs are detected — decrypt first if needed using our Unlock tool, then re-encrypt with new credentials.
- Choose Encryption: Pick algorithm: AES-256 (recommended, strongest) or AES-128 (broader compatibility). Set a strong password (we don't enforce complexity rules, but recommend 12+ characters with mixed case, numbers, symbols).
- Set Permissions: Optional: restrict actions on the PDF even with the password. 'Restrict printing', 'Restrict copying of text', 'Restrict modifications' — these are honored by compliant readers like Adobe and Preview.
- Encrypt & Save: Click 'Encrypt'. pdf-lib + the Web Crypto API encrypt the PDF in your browser. Saves as a new file with the encryption metadata. The original PDF is untouched.
為何選擇此工具
- 100% Local Processing: Files are processed entirely in your browser using JavaScript — never uploaded to any server.
- No Limits: No file count or file size restrictions. Process as many files as your device can handle.
- No Sign-up: Free forever, no account needed, no email required. Open the page and start.
- Private by Design: Nothing is sent to any server. Close the tab and your files are gone forever.
常見問題
How do I add a password to a PDF?
Drop your PDF into our PDF Encrypt tool, choose encryption strength (AES-256 recommended), set a strong password, optionally restrict permissions (printing, copying, modifying), and click 'Encrypt'. The encrypted PDF downloads with your password required to open. Everything happens in your browser — no upload.
Is AES-256 strong enough for commercial use?
Yes. AES-256 is the strongest PDF encryption standard, used by banks, government agencies, and Fortune 500 companies. As of 2026, no practical attack exists. Combined with a strong password (12+ mixed characters), AES-256 encryption provides protection sufficient for confidential commercial documents, legal filings, and medical records.
Can recipients open the encrypted PDF in any reader?
Yes — AES-encrypted PDFs are universally supported. Adobe Acrobat, Preview (macOS), Chrome PDF viewer, mobile PDF apps, and all major readers open these files with the correct password. AES-128 has slightly broader compatibility but slightly weaker protection; AES-256 is preferred for new documents.
Will my PDF be uploaded?
No. Encryption runs entirely in your browser via pdf-lib and the Web Crypto API. The decrypted PDF and your password never leave your device — only the encrypted result saves locally. Even if you lose your password, the original is gone (since it was never uploaded).
Can I set different passwords for opening vs. editing?
Yes. PDF encryption supports two passwords: an 'open password' (required to view the document) and an 'owner password' (controls editing/printing/copying permissions). Most users just need the open password. For sensitive documents where you want recipients to view but not edit without permission, set both.
What happens if I forget the password?
Our tool cannot recover forgotten passwords — neither can anyone else, given proper AES-256 encryption. This is by design (for your security). If you forget the password, the encrypted PDF is effectively inaccessible. Always store the password in a password manager or write it down in a secure location.