Protect PDF
Lock a PDF so only people with the password can open it, and decide what they may do once it is open. Encryption uses AES-256 by default, the strongest method the PDF standard defines.
Protect PDF
or drop PDF files here ·
Max 95 MB per file· Up to 20 files· Deleted after 30 minutes
Files are processed on our servers and deleted after 30 minutes.
Must differ from the open password. Whoever knows it can lift the restrictions.
Low resolution prints a blurry 150 DPI copy, which discourages reproducing the document.
AES-256 opens in Acrobat 9 and every current reader. Choose AES-128 only for very old software.
How to use this tool
- 1
Upload the PDF to protect
Add up to 20 PDFs, each up to 95 MB; the same password protects every file in the batch. Finish editing, signing and flattening first; protection is the last step before sending.
- 2
Choose the passwords
Type an Open password. To limit printing, copying or editing, turn on Restrict printing and editing under Advanced settings and set a different Permissions password.
- 3
Protect and download
Press Protect, download the encrypted PDF, and send the password through a different channel than the file, such as a text message or a phone call.
How do I password protect a PDF?
Upload the PDF, type an Open password and press Protect. The file is encrypted with AES-256 and asks for that password in every reader. To stop printing, copying or editing as well, set a separate Permissions password under Advanced settings.
Open password vs. permissions password
PDF security has two layers. The open password, which the specification calls the user password, encrypts every page, image and attachment so the file is unreadable without it. The permissions password, called the owner password, controls what a reader may do after opening: print, copy text and images, fill in forms, add comments or change pages.
You can use either layer alone or both together. A payslip or medical record needs an open password, because the content itself is private. A published price list or a signed agreement you want people to read but not alter needs only a permissions password with editing turned off. A confidential board pack that must not be forwarded as an editable file uses both.
Under Encryption, AES-256 is the right choice for nearly everyone: it opens in Acrobat and Reader from version 9 onward and in every current browser, phone and desktop viewer. Choose AES-128 only when the recipient uses software old enough to reject 256-bit files, such as an outdated document management system. Encrypt metadata is on by default, which hides the title, author and keywords as well as the pages; turn it off only when a records system must index those fields without knowing the password.
Encryption is only as strong as the password. Use at least 12 characters, avoid names and dates someone could find online, and never send the password in the same email as the file. The full workflow, including how to choose and share passwords, is in how to password protect a PDF. If you later need a copy without protection, unlock PDF removes it with the password you set.
How PDF encryption got stronger
PDF 1.1
40-bit RC4
The first PDF encryption, from 1994. Short keys that can be broken quickly with today's computers.
PDF 1.4
128-bit RC4
Longer keys and finer-grained permissions such as form filling and low-resolution printing.
PDF 1.6
AES-128
The Advanced Encryption Standard replaces RC4 as the recommended cipher.
PDF 1.7 ext. 3
AES-256
Introduced with Acrobat 9 in 2008. The default here; opens in Acrobat 9 and every current reader.
PDF 2.0
AES-256 only
ISO 32000-2 deprecates RC4 and the older schemes and keeps 256-bit AES for new files.
Protect PDF from editing, printing and copying
| Setting | Choices | What the reader can do |
|---|---|---|
| **Printing** | Allowed (default) | Print at full quality |
| **Printing** | Low resolution only | Print a blurry 150 DPI copy, which discourages reproduction |
| **Printing** | Not allowed | No printing in viewers that respect permissions |
| **Allow copying text** | Off (default) or on | When off, text and images cannot be selected and copied; screen readers can still read them |
| **Editing** | Not allowed (default) | No changes at all |
| **Editing** | Fill in forms only | Type into form fields, nothing else |
| **Editing** | Forms and comments | Fill fields and add notes or highlights |
| **Editing** | Any change except extracting pages | Edit freely but not pull pages out into a new file |
| **Encryption** | AES-256 (default) or AES-128 | AES-128 only for very old software |
| **Encrypt metadata** | On (default) or off | Off lets a document system index title and author without the password |
Password protect PDF: dos and don'ts
| Do | Don't |
|---|---|
| Use a passphrase of 12 or more characters | Reuse your email or banking password |
| Send the password by text or phone, the file by email | Use a birth date or name the recipient could guess |
| Keep an unencrypted original in a safe place | Rely on copy restrictions to protect secrets |
| Compress and flatten before protecting, not after | Turn off Encrypt metadata unless an indexing system needs it |
TipFor a document many people must read but nobody should change, skip the open password and set only a Permissions password with Editing on Not allowed.
Protect PDF questions
How do I protect a PDF with a password for free?
Upload it, type an Open password and press Protect. The downloaded copy asks for that password in every PDF reader, including Acrobat Reader, Chrome, Edge, macOS Preview and the iPhone Files app.
How do I protect a PDF from editing but let people read it?
Leave Open password empty if anyone may read it, turn on Restrict printing and editing, set a Permissions password and choose Not allowed under Editing. Readers open the file normally, but compliant viewers block changes until someone enters the permissions password.
Why must the permissions password differ from the open password?
Whoever knows the permissions password can lift every restriction. If it matched the open password, everyone you gave the open password to could also remove the limits, which would make them pointless.
What happens if I lose the open password?
The file cannot be opened. AES-256 has no recovery mechanism or back door, and that is the point of it. Keep the password in a password manager and keep an unencrypted original somewhere safe.
Are print and copy restrictions secure?
They are a policy, not a lock. Acrobat, Chrome and other mainstream viewers respect them, but a viewer that ignores them can still print or copy once the file is open. For confidential content, rely on the open password, not on restrictions alone.
Should I flatten a PDF before protecting it?
If it contains filled form fields or comments that must not change, yes. Use flatten PDF first, then protect the flattened copy, so the answers are part of the page even for someone who later gets the permissions password.
Does encryption make the PDF bigger?
Barely. AES encrypts the existing content stream by stream and adds a small security dictionary, so the size stays about the same. Compress the PDF before protecting it if you need it smaller, because an encrypted file cannot be recompressed without the password.
Can I password protect a PDF on my phone?
Yes. This page works in Safari and Chrome on iPhone and Android: pick the PDF from Files or Downloads, type the password and press Protect. The encrypted copy saves back to your phone and asks for the password when opened in any app.
| Flatten PDF | Compress PDF | Merge PDF |
| Unlock PDF | PDF to PDF/A | Split PDF |