A bank statement, a payslip, a medical record, a contract: a PDF sent by email travels in the clear and stays readable by anyone who gets hold of it. Protecting it with a password is simple, provided you know what each setting really protects, because one of them encrypts the content and the other is merely a courtesy that many programs ignore.
Two very different protections
A PDF can carry two kinds of lock, and mixing them up is the most widespread mistake:
| Open password | Restrictions (print, copy, edit) | |
|---|---|---|
| What it does | Encrypts the content: without the password, the file is unreadable. | Politely asks the PDF reader to disable certain actions. |
| Strength | Real, with a good password. | Weak: common readers honour them, but software can bypass them. |
| Use it for | A confidential document. | Discouraging accidental copying or printing, never for protecting a secret. |
If the content is sensitive, the open password is the only setting that matters. A PDF “protected” by restrictions alone opens freely.
Protecting a PDF step by step
- Open Protect PDF and drop the file (200 MB maximum).
- Enter a strong open password (see below) and, if you wish, tick the restrictions to apply: printing, copying, editing.
- The optional “owner” password lets you change the restrictions later; left empty, a random one is chosen.
- Run the encryption and download the file. The encryption is AES-256 (the PDF 2.0 standard), computed on your device.
- Test: open the protected file and check that the password is requested and accepted, before sending it.
The password is neither sent nor stored. If it is lost, it cannot be recovered: keep it in a password manager.
Choosing a password that really protects
Strength is measured in bits of entropy: each extra bit doubles the number of guesses an attacker needs. A few reference points you can calculate yourself:
- 8 lowercase letters: 26⁸ ≈ 2.1 × 10¹¹ possibilities, about 37.6 bits. That is within reach of a motivated attacker who holds the file and suitable hardware.
- 12 characters drawn at random from the 94 printable keyboard characters: about 78.7 bits, out of practical reach.
- A 5-word passphrase drawn at random from a list of 1,000 words: 5 × log₂(1,000) ≈ 49.8 bits, easier to remember; 6 words give about 59.8 bits.
A dictionary word, a birth date or “password2024” does not have the entropy its length suggests. Generate yours with Password Generator and read Strong passwords: entropy, passphrases and data breaches.
Passing on the password without exposing it
Sending the file and its password in the same email cancels the protection: anyone intercepting the message has both. Use another channel (a text message, a call, an instant message) and, ideally, agree on the password beforehand.
Unlocking a PDF: when it is legitimate
Received a protected statement and tired of retyping the password each time you open it? Unlock PDF produces a copy that opens without asking for anything, provided you type the password once. The tool guesses nothing and breaks no protection: without the right password there is no result, and that is deliberate.
If the PDF opens freely but forbids printing, copying or editing, those restrictions are lifted without a password, since they rely on the reader's goodwill. The page content is not modified: the file is simply rewritten without encryption.
Use this feature only on documents whose protection you are entitled to remove. Lifting the restriction on a document whose author expressly forbids copying may breach its licence or the law of your country.
Common mistakes
- Believing a PDF with restrictions alone is confidential.
- Choosing a short password “because it's just a PDF”.
- Forgetting the password: no support, here or elsewhere, can recover it other than through long and uncertain attacks.
- Protecting then deleting the original without having tested the protected file.
- Relying on protection to hide text mistakenly left in a file already sent: once distributed, a file cannot be taken back.
Honest limits
- An old reader may not handle AES-256 encryption: test with the recipient's software.
- Encryption protects the file, not the device: a virus on your computer sees the document once it is open.
- Compressing or merging a protected PDF requires unlocking it first; apply protection last.
Frequently asked questions
Is my password sent to MaxyTools?
No. Encryption is computed in your browser; neither the password nor the file leaves your device.
I forgot my PDF's password: what can I do?
Try the usual passwords you may have used and check the original emails; the sender can also resend the file. Our tools neither guess nor bypass any password.
Is AES-256 strong?
Yes: the algorithm is not the weak link. Security depends mainly on the quality of the password you choose.
Can a PDF whose printing I disabled still be printed?
In most readers no, but these restrictions are not encrypted and some programs ignore them. Only the open password guarantees confidentiality.
Does the PDF's content change when I protect or unlock it?
No. Pages are untouched; only the encryption is added or removed.