Merging a password-protected PDF fails with an error saying the PDF is encrypted and cannot be merged. The encryption stops any tool from reading or copying the file. Remove the password first. You can do this only if you know the password and own the file. There are two types of PDF passwords. Check the file's protection settings, then remove the password so you can complete your merge.

Two Types of PDF Passwords

PDF protection uses two separate passwords. Knowing which one your file has tells you what you can do with it.

  • User (open) password: You need this to view the file at all. Without it, you cannot open the PDF. This is the password you type when you first click the file.
  • Owner (permissions) password: This password controls what you can do after opening the file. It restricts printing, copying text, or editing. You might be able to view the file but not select text or print it.

When a tool says it cannot merge the file, it usually means the file has a user password that has not been entered. After you open the file with the correct password, the owner password may still block some operations. Remove both types of protection before merging.

How to Check Security Settings

Check what kind of password your PDF has without guessing. In Adobe Acrobat Reader, go to File > Properties > Security. The Security tab shows the Security Method and lists which actions are allowed or disallowed. If the method says "Password Security" and the user password is required, you will see that. If only the owner password is set, you will see restrictions on printing or editing but you can still open the file.

Checking the protection settings helps you decide which removal method to use. If the Security Method shows "No Security," the file is already unlocked and can be merged directly.

Legitimate Ways to Remove a PDF Password You Know

Once you know the password and own the file, you have several ways to remove the protection. Only remove passwords from documents you own or are authorised to change. Three reliable methods follow.

Using Adobe Acrobat Pro

  1. Open the PDF in Adobe Acrobat Pro. Enter the password when prompted.
  2. Go to File > Properties > Security.
  3. In the Security Method dropdown, select "No Security."
  4. Click OK and save the file. The PDF will no longer have a password.

Using Preview on Mac

  1. Open the file in Preview. You will need to enter the user password to open it.
  2. Go to File > Export.
  3. In the export dialog, untick the box that says "Encrypt."
  4. Choose a location and save the new copy. This copy will have no password.

Using Google Chrome

  1. Open Google Chrome. Drag the PDF into the browser window or use File > Open.
  2. Enter the password when prompted so you can view the PDF.
  3. Click the three-dot menu (or press Ctrl+P on Windows, Cmd+P on Mac) and select Print.
  4. In the Destination dropdown, choose "Save as PDF."
  5. Click Save. The new PDF will be an unencrypted copy with no password.

What to Do If You Forget the Password

If you do not know the password, there is no legitimate way to remove it. PDF encryption is designed to prevent access. You cannot bypass the protection without the password. Contact the document owner or recreate the file from the original source. Do not use third-party services that claim to crack passwords. They may violate copyright or privacy laws.

Merging After Removing the Password

After you have removed the password using one of the methods above, you can merge the PDF with other files. The file will no longer show the "pdf is encrypted cannot merge" error. Upload it to any online or offline tool. For example, use mergepdfonline.net to combine PDFs into one document free and online with no watermark. Upload the unlocked files and start the merge.