I have a password protected PDF file. I know the password but in order to share the file, I have to remove the password from the PDF and share an unprotected copy. How can I do this in Ubuntu with or without the GUI?
The easiest way GUI (recommended for novice)
Open the protected file and use ctrl+p or use print option to print the file, now save the file as pdf.
Using Command line
If you have pdftk already installed you can skip step1
Step 0: To check if Pdftk is already installed
sudo apt list | grep pdftk
If output contains '[installed]' tag with pdftk then you can skip step1 i.e if the output is like this
pdftk/xenial,now 2.02-4 amd64 [installed]
Step 1: Install pdftk
sudo apt get install pdftk
Step 2: Run following command
pdftk /path/to/input.pdf input_pw <yourpassword> output out.pdf
If you don't want to install pdftk there is another utility qpdf which is automatically installed (at least on 16.04 which I am using)
To use qpdf for generating unsecured pdf run following command.
qpdf -password=<your-password> -decrypt /path/to/secured.pdf out.pdf
For detailed information take a look at this HTG tutorial