or drop a file anywhere here
Files other than PDF are converted first. Signing in raises the size limit.
Protect PDF puts a password on a PDF. Add your file, type a Password to open, and type it again in Confirm password. A line under the first box reads Weak, Fair or Strong password. It is a hint only and never blocks you. The panel states that anyone who opens the PDF will need the password and that the file is encrypted with AES-256. To control what people can do once the file is open, switch on Also limit what people can do. That adds a Permissions password and six checkboxes: print, copy text and images, edit the content, add comments, fill in forms, and add, remove or turn pages. Everything stays allowed until you untick it, and at least one must be off. Some PDF readers ignore these limits, so the password to open is what keeps the file private. It suits a file you send to a known person: a statement, a form, a draft. It does not make a weak password strong, and it cannot stop someone you gave the password to from copying what they can read. In our test of a three-page PDF, the copy was ready about four seconds after we pressed Protect PDF.
Our own 3-page A4 invoice-style PDF, English text, 3,215 bytes, not encrypted before
Type the password in Password to open and again in Confirm password. If the two differ, the panel says the passwords do not match and Protect PDF stays off. A file with this password asks for it every time someone opens it.
The panel says the file is encrypted with AES-256. There is no setting to choose a weaker or different method. In our test we read the encryption dictionary of the downloaded copy with qpdf: version 5, revision 6, key length 256, AES for streams, strings and the file.
Switch on Also limit what people can do, type a Permissions password, and untick print, copy text and images, edit the content, add comments, fill in forms, or add, remove or turn pages. The Permissions password must differ from the one to open, and you need it to lift the limits later. In our test, with only Print and Copy unticked, printing and copying were refused, extraction for accessibility stayed allowed, and the edit, comment and page-assembly flags stayed allowed.
With limits on, Password to open is optional. Leave it empty and anyone can open the file, but only the Permissions password lifts the limits. This is also what Change permissions does. In our test such a copy opened without any password prompt and the Permissions password was reported as the owner password.
| You want | Fill in | What the copy does |
|---|---|---|
| A file only people with a password can open | Password to open and Confirm password | Readers ask for the password before showing the file. Every permission stays allowed. The same password also acts as the owner password, so nothing is restricted. |
| The same, with some actions switched off | Also limit what people can do, a Permissions password and your unticked boxes, plus the password to open | Readers ask for the password to open. The actions you unticked are switched off for readers that honor limits. |
| A file anyone can open, with printing or copying switched off | Also limit what people can do and a Permissions password, with Password to open left empty | Anyone can open and read the file. Readers that honor limits refuse the actions you unticked. |
Drop one PDF on the upload area at the top of the page, or click to choose it.
Type Password to open and repeat it in Confirm password. For limits, switch on Also limit what people can do, type a Permissions password that differs from the first, and untick what you want to block.
The button fills with the job's progress and the steps show under it. When it says Done, the editor holds the protected copy: press Download PDF, or Undo to go back. Open the copy once and type the password to check it works. In our test the button went from the click to Done in about 4 seconds.
The panel shows only what the file will do. The password is typed twice, so a typo does not lock you out. The limits have their own switch, their own password and six named boxes, and the panel refuses a setup that limits nothing or reuses the open password as the permissions password. It also says plainly that some readers ignore limits and that the password to open is what keeps the file private. You can protect a file without signing in, within the free daily limit and the free file size limit.
| What you see | Why | What to do |
|---|---|---|
| Protect PDF stays off | The two passwords differ, or with limits on there is no Permissions password, or nothing is unticked | Read the line under the boxes: it names what is missing. |
| The panel says to use a different password | The Permissions password is the same as the Password to open | Choose a different Permissions password. |
| Printing or copying still works in some programs | Some readers ignore limits | Rely on the password to open for real protection. |
| A reader asks for a password I did not mean to set | You typed one in Password to open | To limit actions on a file anyone can open, leave that box empty and use the limits. See Change permissions. |
| A later step on the protected copy asks for a password | The copy needs its password before a program can read its pages | Protect the file as the last step. |
| The preview after Done looks unprotected | In our test the editor kept showing the original in its preview | Press Download PDF and open the downloaded file. It should ask for the password. |
| An upload form says my PDF is password protected, but it opens freely | A copy with only a Permissions password opens without a prompt but is still encrypted, and some upload forms reject any encrypted file | Use Unlock PDF on a copy, or set no limits for files that go to such forms. |
| Job | What it stops | What it does not stop |
|---|---|---|
| Protect PDF with a password to open | A reader cannot open the file without the password | Someone who has the password can do everything. In our test all permissions stayed allowed. |
| Protect PDF with limits and no password to open | Readers that honor the flags refuse the actions you unticked | Anyone can open and read the file. Per the qpdf manual, the reading software enforces restrictions; the encryption does not. |
| Change permissions | The same limits panel, opened with limits already on | The same gaps as above: it limits actions and leaves the content readable. |
| Unlock PDF | Removes the password from a copy, when you know it | It does not add protection. Use it before you protect again with a new password. |
You email invoices, tax forms and statements that carry account numbers. A password to open keeps the attachment unreadable if the message lands in the wrong inbox.
You send offer letters and payroll summaries to one person at a time. Protect each file and share its password through another channel, such as a phone call.
You want a client to read a report on screen. Set a Permissions password and untick Print and Copy text and images, knowing that a reader that ignores limits will still allow them.
Facts checked on November 5, 2026
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AES-256. The panel states it, and there is no setting that changes it. In our test the downloaded copy read as version 5, revision 6, key length 256 in qpdf.
The password to open is needed to read the file. The permissions password is only asked for when someone wants to lift the limits you set, such as the ban on printing.
Yes. Switch on Also limit what people can do, leave Password to open empty and set a Permissions password. Anyone can then open the file, and only that password lifts the limits. Change permissions opens the same panel with limits already on.
No. The panel warns that some PDF readers ignore them. Treat them as requests. In our test with Print and Copy unticked, extraction for accessibility stayed allowed.
indox has no way to recover it. Keep your original file or store the password in a password manager.
It shows a hint: Weak, Fair or Strong. Longer passwords that mix kinds of characters read as Strong. The hint never blocks you.
Protecting writes a new encrypted copy, so a certificate signature may not survive. Check it in your PDF reader and keep the original signed file.
No sign-in is needed to get a protected copy. The free daily limit and file size limit still apply.
Yes. Run qpdf --show-encryption on the downloaded file. For our test copy it reported R = 6, key length 256 and AESv3 for streams, strings and the file. The qpdf manual explains each line.
A file with only a permissions password opens without a prompt but is still encrypted, and some upload forms reject encrypted files. Unlock a copy with Unlock PDF or protect it without limits.