PDF password protection explained: encryption vs permissions

If you want a PDF to require a password before someone can read it, set an open password. Options such as “do not print” and “do not copy” govern what a cooperating reader allows after opening the file. They do not stop someone who can read the content from making another copy of it.

Check what protection a file actually has

Close the document and reopen it in a reader that has not already remembered the password. Then inspect its security properties if the reader offers them.

Behaviour	What it tells you
A password is required to display the pages	Opening is password-gated; check the encryption method separately
It opens without a prompt, but copying or printing is restricted	Reader-enforced permissions may be set
It prompts, then restricts copying or printing	Opening protection and permission flags may both be present

A prompt alone does not tell you whether the password is strong or the encryption method is suitable. A missing prompt can also mean the reader has cached the password.

The two passwords and the important distinction

The PDF standard security handler uses a user password, often called the open password, and an owner password, often called the permissions password. Either can provide access to the encryption key; conforming readers may apply different restrictions depending on which was used.

A permissions-only PDF can still be encrypted. It commonly uses an empty user password, allowing the reader to decrypt it without asking you for a secret. The important limitation is that anyone who can open it has access to its contents, while printing and copying restrictions depend on the reader’s enforcement.

That is why a greyed-out Copy button should not be treated as protection for confidential information. It describes that reader’s behaviour, not a guarantee about every program that can open the file.

Using Protect PDF on this site

The Protect PDF tool accepts an unprotected PDF, asks for a password and confirmation, and offers Suggest a strong password. Save the password before choosing Protect PDF: the form clears it after producing the download.

The printing and copying switches are labelled as advisory. The tool uses the same value for the user and owner passwords, so they are not separate secrets you can distribute to different people.

There is also a limitation in the current implementation: the page displays AES-128, but it lets the PDF library select encryption from the input PDF version rather than explicitly selecting AES-128 for every file. Older PDF versions can take a different path. Do not use the page label as proof of the downloaded file’s algorithm. Check the saved file’s security details; if you need a specified encryption standard, use a workflow that explicitly selects and verifies it.

Open the saved copy with the intended password, check that an incorrect password is rejected, and confirm the pages still work in the recipient’s reader. Keep the original in an appropriate private location.

Choose a password that is hard to guess

Someone holding an encrypted PDF can attempt password guesses offline; there is no website login rate limit to slow them down. Use a unique, random password stored in a password manager, or a suitably long randomly generated passphrase. The password generator is another way to create one.

The strength display for a typed password estimates from its length and character types. It does not know whether you typed a predictable phrase, a reused password or random characters. Treat it as a rough indication, not a security assessment.

ToolsNow cannot look up or reset the document password for you. Guessing tools may recover short or predictable passwords, so “no reset” does not mean every forgotten password is unguessable.

What the encryption names mean

RC4-based PDF encryption is obsolete and should not be selected for new confidential documents. AES-128 and AES-256 name different key sizes, but the PDF security-handler revision and password processing also matter. Modern revision-6 AES-256 is distinct from older AES-256 arrangements.

A longer key does not rescue a predictable password. Nor does encryption remove visible private information, metadata or attachments: it controls access to the protected contents. Once a recipient opens them, they can share what they have read.

For a handoff, send the password through a separately agreed channel rather than alongside the file in the same message. That reduces the chance that one forwarded or exposed message contains both.

Removing a password also has an export trade-off

The PDF unlock tool opens a supported document with the password you supply and rebuilds its pages as images. It is not a password-recovery service.

The resulting PDF opens without that password, but it loses the existing searchable text layer, interactive features and digital-signature verification. A visible signature image is not the original digital signature. If you need to retain those features, use an authorised PDF editor that can remove encryption without rasterising the pages.

Sources and further reading

• ISO 32000-2 / PDF 2.0 — encryption and the standard security handler
• NIST FIPS 197 — AES specification
• NIST SP 800-63B — earlier Digital Identity Guidelines, retained for background
• qpdf documentation — encryption, empty passwords and reader-enforced permissions

Last reviewed 2 October 2026.