To remove a password from a PDF file in Linux, you can use the pdftk tool. This tool allows you to manipulate PDF files from the command line, including removing passwords.
First, install pdftk using your system's package manager. For example, on a Debian or Ubuntu system, you can use the following command:
sudo apt-get install pdftk
Next, navigate to the directory containing the PDF file you want to remove the password from. Then use the pdftk command with the input_file.pdf and output_file.pdf options to specify the input and output PDF files, respectively. Finally, use the decrypt option to remove the password from the PDF file.
For example, to remove the password from a PDF file named "input_file.pdf" and save the result to a new file named "output_file.pdf", you can use the following command:
pdftk input_file.pdf output_file.pdf decrypt
This will remove the password from the PDF file and save the result to a new file. You can then view the PDF file without a password.
Note that this method only works if you know the password for the PDF file. If you do not know the password, you will not be able to remove it using pdftk.