不使用 Adobe 为 PDF 设置密码保护的方法：浏览器分步指南（2026）

AES (Advanced Encryption Standard) at 256-bit key length. AES is the encryption standard adopted by the U.S. government for top-secret information and used by banks, financial institutions, and security agencies worldwide. It is the modern PDF encryption standard, supersedes the older RC4 algorithm used in legacy PDFs, and is computationally infeasible to brute-force with current technology. When you protect a PDF with iHatePDF, it gets the same protection level as the most security-conscious institutions use.

Very strong when paired with a strong password. AES-256 encryption itself is essentially unbreakable with current computing power. The only realistic attack is guessing the password. So password strength is everything: an 8-character password with random characters might take days to crack with modern hardware, while a 16-character mixed password would take longer than the age of the universe. The tool accepts 4 to 20 characters (standard keyboard characters); use the full length, mixing uppercase, lowercase, numbers, and symbols, for the strongest result.

There is no recovery. PDF password recovery is computationally infeasible by design (the whole point of encryption). Do not lose the password. Best practice: store it in a password manager (1Password, Bitwarden, LastPass, Apple Keychain, Google Password Manager) immediately after setting it. If the PDF is for someone else, share the password through a separate secure channel (different email, encrypted messenger, phone call) so the password and file never travel together.

Length and randomness. Better than "Password123!": a random 16 to 20 character string mixing upper, lower, numbers, and symbols (the tool caps passwords at 20 characters, so favour randomness over a long phrase). Avoid: common words, personal info (birthdays, names), keyboard patterns (qwerty, asdf), and any password you use elsewhere. The strongest passwords are ones you cannot remember, generated by a password manager. The best protection is one strong, unique password per protected file, stored safely.

Yes. The PDF is encrypted using the standard PDF encryption format. Anyone with the password can open it in Adobe Acrobat, Adobe Reader, Preview on Mac, Chrome browser PDF viewer, Edge, Firefox, mobile PDF readers (Apple Files, Google Drive viewer, Adobe Reader mobile, Foxit, PDF Expert), and any other standards-compliant PDF software. The recipient does not need iHatePDF or any special tool. They just need the password.

Yes, with a free account. Sign in to your free iHatePDF account and you can batch process up to 3 PDFs simultaneously (80 MB each, 120 MB total). Apply one shared password to all of them, or set a different password for each file. Useful when sending a packet of related sensitive documents (tax returns and supporting forms, a contract and its appendices, three months of bank statements). Each file gets its own encrypted copy and the batch comes back as a ZIP. Without an account, protect one PDF at a time (up to 80 MB).

Yes. Below the password you can uncheck Allow printing, Allow copying, or Allow editing. Those limits are written into the PDF and enforced with a separate random owner key, so standards-compliant readers (Adobe Acrobat, Preview, most browsers) honour them. Keep in mind PDF permission restrictions are advisory - a determined user with the open password could find software that ignores them - so treat them as a courtesy control, while the open password is the real security barrier.

Yes. Click the cloud icon during upload and authenticate once with your cloud provider. After that, browse cloud folders and select PDFs directly. The encrypted PDF can be saved back to the same cloud location with one click. The password never leaves your browser session, only the encrypted file is stored.

No. The password you set is used to encrypt the file during the conversion job and is discarded immediately after. We never store, log, transmit to third parties, or share your password. If you lose the password, we cannot help recover it because we never had it. This is by design: storing passwords would defeat the security model.

Yes. Files upload over HTTPS, encrypt on our secure servers, return to you as protected PDFs, and the original files delete automatically at the end of your session. No human review, no AI training, no third-party sharing. GDPR-compliant. The combination of HTTPS transport, fast deletion, and zero password storage means iHatePDF is safe for the most sensitive content: tax returns, medical records, legal documents, financial statements.

Yes. Works in any modern mobile browser (Safari on iPhone, Chrome on Android, Firefox, Edge, Samsung Internet). Upload PDFs from your phone storage or cloud, set a password, download the encrypted PDF. Useful when you receive sensitive documents on your phone and need to protect them before forwarding via email or messaging.

Yes if you have the password. Use Unlock PDF to remove protection: upload the encrypted PDF, enter the current password, download the unprotected version. If you do not have the password, removal is not possible (the security model would be broken otherwise). For protection you may want to reverse later, store the password securely so future you can unlock it.

No. No watermarks, no signup gate for single conversions, no daily caps. The PDF is just your original document with AES encryption added. iHatePDF makes money through optional Pro features, not by watermarking free tool output.

Because email forwards happen, files get copied, devices get lost or shared, and sensitive PDFs end up in unintended folders. Password protection adds a hard barrier: even if the file lands somewhere it should not be, the contents remain unreadable. Critical for tax returns with social security numbers, salary spreadsheets, medical records, legal documents, business plans, customer lists, and any other content that could cause real harm if seen by the wrong person.