Portable Document Format (PDF) files are essential for sharing documents across different platforms. They preserve formatting and ensure consistency, making them widely used in both personal and professional settings.

The PDF format supports password-based encryption to protect sensitive information. However, managing multiple passwords for various files can become cumbersome, especially when organizing large collections of documents for projects or financial records.

This guide walks you through the process of removing a password from an encrypted PDF in Linux. Additionally, it covers techniques to recover a forgotten password.

Table of Contents

• Removing the Password from an Encrypted PDF
• Cracking a PDF Password with pdfcrack
• Frequently Asked Questions

Tip: need to sign a PDF on your mobile device? Check out how you can easily add your signature to a PDF using your Android phone.

Removing the Password from an Encrypted PDF

A straightforward method to eliminate a password from a secured PDF is by using the “Print to PDF” feature available in most document viewers. PDF encryption only applies when the file is stored—once opened, the content is decrypted in memory.

This allows you to save a clean, unencrypted version simply by printing the document to a new PDF file.

1. Launch the encrypted PDF using your preferred PDF reader.
2. When prompted, enter the correct password to access the document.

3. Open the application’s main menu.

4. Choose the Print option or click the printer icon.

5. In the print dialog, select “Print to File” from the available destinations.

6. Make sure the output format is set to PDF near the filename input field.

7. Click “Print” to generate and save the decrypted PDF.

Good to know: this “print to PDF” functionality is also available on Android devices.

Removing a PDF Password via Command Line

You can also decrypt a PDF directly from the terminal, which is ideal for automation or batch processing.

Start by installing qpdf, a powerful tool for manipulating PDFs. On Ubuntu, run:

<code>sudo apt install qpdf</code>

Navigate to the folder containing your encrypted file and execute:

<code>qpdf --password=maketecheasier --progress --decrypt ./encrypted.pdf ./output.pdf</code>

To decrypt all PDFs in a directory, use this shell script:

<code>mkdir ./output<br>for i in *.pdf; do qpdf --password=maketecheasier --progress --decrypt "${i}" ./output/"${i}"; done</code>

Good to know: after decryption, you can merge multiple PDFs into a single file with ease.

Brute Forcing a PDF Password Using pdfcrack

The methods above work only if you know the password. But what if you’ve forgotten it—especially with older files?

In such cases, pdfcrack comes in handy. It attempts to recover the password through brute-force or dictionary attacks by testing combinations until the correct one is found.

Install pdfcrack on Ubuntu with:

<code>sudo apt install pdfcrack</code>

Navigate to your PDF’s location and run:

<code>pdfcrack -f ./encrypted.pdf</code>

Be aware: this process may take a long time. Complex passwords with numbers, symbols, and mixed cases could require hours to crack.

Speed things up by using a custom wordlist—a text file containing likely passwords. Use it like this:

<code>pdfcrack -f ./encrypted.pdf --wordlist=/home/$USER/Documents/passwords.txt</code>

You can also narrow down the search by setting constraints. For instance, the command below limits guesses to 12 or 14 characters using only specific letters:

<code>pdfcrack -f ./encrypted.pdf --charset="sqmweartkcyuihop" --minpw=12 --maxpw=14</code>

Alternatively: if you're looking to create strong, secure passwords, here are some reliable online tools to generate them.

Frequently Asked Questions

Can I apply the same encryption settings from one PDF to another?

Yes. Using qpdf, you can copy encryption properties from an existing PDF. This is helpful when automating encryption for multiple files with the same password.

Use this command:
qpdf ./new.pdf --copy-encryption-file=./encrypted.pdf --encryption-file-password=mysuperpassword ./output.pdf.

What are the drawbacks of using “Print to File”?

A major limitation is that the resulting PDF will no longer contain selectable text or form fields. The output becomes a static document—often just a series of images—so you can't extract or edit text.

I stopped pdfcrack by mistake. Can I resume where I left off?

Yes. pdfcrack automatically saves a state file upon exit, recording the last attempted password and progress. To continue, use:
pdfcrack -f ./encrypted.pdf --loadstate=./savedstate.sav.

Image credit: 123RF. All edits and screenshots by Ramces Red.

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