How to add or remove a PDF password (one you know)

A PDF can have two kinds of password: an open password that’s asked for when you open the file, and a permissions password that restricts printing and editing after it’s open. Either way, you need to know the password to remove it. And if you forget a password you set yourself, you can’t open the file either. This guide explains the difference between the two, how to unlock a PDF you received with a password you know so you can submit it, and how to add a password to your own PDF.

Open password vs permissions password

The PDF format calls them the user password and the owner password. Apps usually show them as an open password and a permissions password.

Kind	Open password (user password)	Permissions password (owner password)
When it’s used	When you open the file	When you lift or change the restrictions
What it blocks	Viewing the content at all	Actions like printing, editing and copying
If you open the file with it	The document’s restrictions apply	Everything is allowed, with no restrictions

According to the qpdf documentation, a PDF app is supposed to obey the restrictions when a file is opened with the user password, but not when it’s opened with the owner password. A PDF with only a permissions password has an empty user password, so anyone can open it. The same documentation explains that these restrictions are enforced only by the software that opens the file. So if you want to keep the content itself private, set an open password, not just a permissions password.

You need to know the password

A PDF with an open password is stored encrypted, so you need either the open password or the permissions password to unlock it. Unlock PDF follows that rule too.

• When you add a file, it checks which kind of password the PDF has, then opens it once with the password you enter. It never guesses passwords or tries one after another.
• A PDF with only a permissions password still needs that permissions password. Opening without a password prompt doesn’t mean it can be unlocked without one.
• A PDF with an open password can also be unlocked with its permissions password.
• If the password is wrong, you’ll see “The password doesn’t match”. Check uppercase, lowercase and spaces, type it again, and try again on the same file.

PDFs whose password you don’t know can’t be unlocked. If someone sent you the file, ask them for the password or for a new copy. If you locked the file yourself and forgot the password, you’ll need the original without a password. That’s why it’s safer to keep the original when you add a password.

Unlocking a pay stub or tax form to submit it

Documents like pay stubs or tax forms sometimes arrive locked with a password chosen by the sender, such as one based on your date of birth. But the place you’re submitting to may want a file without a password, or you may need to combine several documents into one PDF. Merge PDF leaves out password-protected PDFs with “Password-protected PDFs can’t be processed”, so unlock them before you merge.

1. Check the sender’s notice or email for the password rule.
2. Use Unlock PDF with that password to make a copy without a password. The original file doesn’t change.
3. If you need to submit everything as one file, merge the unlocked files. For what to check first, see what to check before merging PDFs.

Anyone can open the unlocked copy. If it contains personal information, don’t leave it in shared folders or on a shared computer, and delete copies you no longer need once you’ve submitted it. The result’s name gets -unlocked added, so if the recipient asks for a specific file name, rename it after saving.

How to add a password to your own PDF

When you add a password, choose AES-256. The qpdf documentation says 256-bit encryption always uses AES, and that this method (R6) is the only one of the standard options that isn’t deprecated in the PDF 2.0 specification. You can add a password with apps you may already have:

• Word: when you save as PDF, choose “Encrypt the document with a password” in the options. As Microsoft Support explains, only people with the password can then open the PDF.
• Preview on Mac: choose File → Export, click Permissions, select Require Password To Open Document, and enter the password twice. You also have to enter an owner password twice, and on the same screen you choose whether printing and changes are allowed without it.
• Protect PDF: enter the same password in Open password and Confirm password, and the file is locked with AES-256. The permissions password is set to the same value, so anyone who opens the file with the password can print, copy and edit it.

When we locked a 3-page test PDF (2 KB) with Protect PDF, it produced a-3p-protected.pdf (2 KB), which wouldn’t open without the password. Adding it to Unlock PDF with the same password brought back all 3 pages. (Measured in desktop Chrome; results vary by device and browser.) Short passwords are easier to guess, so choose a long one, and send the file and the password through different channels.

How to do it with ZEKILO Studio

Unlock PDF removes the password inside this browser. Your file and the password you enter never leave your device, and the password isn’t saved.

1. Drag and drop one password-protected PDF or pick it with [Choose files]. Depending on the password, you’ll see either “Enter the open password” or “Enter the permissions password”.
2. Enter the password you know and press [Start]. You can check what you typed with [Show].
3. Save the PDF without its password using [Download]. A file named contract.pdf is saved as contract-unlocked.pdf.

A test PDF (3 pages, 2 KB) with both an open and a permissions password was unlocked with its open password, and a PDF (3 pages, 2 KB) with only a permissions password was unlocked with that password. Both became 3-page PDFs without a password (2 KB). (Measured in desktop Chrome; results vary by device and browser.) You can add one PDF at a time. We recommend up to 200 MB on desktop and 50 MB on mobile. Files over 500 MB aren’t processed.

Summary

• An open password blocks opening the file; a permissions password blocks actions like printing and editing. To keep the content private, you need an open password.
• You can only remove a password you know. A PDF with just a permissions password still needs that password.
• If you unlock a document to submit it, handle the unlocked copy with care and delete it when you no longer need it.
• Lock your own PDFs with an AES-256 open password, and keep the original and the password safe, because a forgotten password means a file you can’t open.