How to remove passwords from PDF files

Recently, a financial institution emailed me a password-protected PDF file. Handling such PDFs was a nuisance. First, I had to call them to obtain the password. Second, because that was a file I'd like to access in the future, I needed to record the password, unless … I could somehow remove the password from the PDF file.

This post outlines several ways to remove a password from a PDF.

pdftk

pdftk is my go-to tool for manipulating PDFs. To save a password-protected PDF into a new file, without the password, simply execute a command like this:

$ pdftk MyInput.pdf input_pw PASSWORD output MyOutput.pdf
WARNING: The creator of the input PDF:
   MyInput.pdf
   has set an owner password (which is not required to handle this PDF).
   You did not supply this password. Please respect any copyright.

You can safely ignore the warning message.

An encrypted PDF file can have up to 2 passwords, the user password and the owner password, with the latter having more privileges. Either password will let you perform the operation, although pdftk prefers the owner password if the PDF has one. If you did not create the original PDF, most likely, the password given to you was the user password. Hence the warning.

Security conscious users would balk at specifying the plain-text password on the command line. Specifying the do_ask parameter allows you to enter the password via standard input.

$ pdftk MyInput.pdf output MyOutput.pdf do_ask

qpdf

An alternative solution is to use qpdf. For instance,

$ qpdf --decrypt --password=PASSWORD -- MyInput.pdf MyOutput.pdf

Note that the marker -- is used to separate the options from the input and output filenames.

To hide the password from the command line, specify the @- argument, which enables you to enter arguments via standard input. When prompted, enter --password=PASSWORD.

$ qpdf --decrypt @- -- MyInput.pdf MyOutput.pdf

Alternatively, you can specify the password inside a file, for instance, @/home/peter/arguments.txt. Note that the filepath is appended to the single character @. The file contains the line --password=PASSWORD.

$ qpdf --decrypt @/home/peter/arguments.txt -- MyInput.pdf MyOutput.pdf

pdftops/ps2pdf

This solution is more involved than the first 2: first convert the PDF to Postscript, and then back to PDF. I include it here to show an alternative approach, and it is probably not something you will actually do.

1. To convert it to Postscript:
   

   
   $ pdftops -upw PASSWORD MyInput.pdf MyInput.ps
   
   

   Note that -upw refers to the user password. If you have the owner password instead, replace -upw with -opw.
   
2. To save it back to PDF:
   

   
   $ ps2pdf MyInput.ps MyOutput.pdf