Some PDFs you download are write protected. This is especially annoying if you do like to mark up the PDF in a utility like e.g. DEVONthink. It is not even possible to simply highlight something as long as the PDF is write protected.
Luckily the problem can be solved with a little command line application called qpdf.
Installation
There are multiple ways to install the software. You can either use the package manager of your operating system or you can use Docker. This will allow you to quickly use the command and discard the whole execution environment if you no longer need it.
Homebrew
I’m on a Mac and if you have Homebrew installed, you can execute brew install qpdf in your terminal application. This will download and install the qpdf command line tool that you can use to remove the PDF write protection.
Note
I’m running the following version:
#$> qpdf --version qpdf version 10.0.1 Run qpdf --copyright to see copyright and license information.
Keep this in mind if a feature is not available or does not work.
If you’re not on a Mac you need to use the package manager of your operating system to install the application.
You can use the utility like so:
#$> cd folder-with-pdf
#$> qpdf --decrypt --replace-input my.pdf
Docker
If you are already using Docker then why not employ a container to get the job done. The container I am using is pretty heavyweight if you just need to use the little qpdf utility and you may want to use a smaller container. However, if you’re additionally documenting stuff with Sphinx or use Pelican to write your blog, the heavyweight container might be a good choice for you anyway.
You can use the custom Sphinx container as follows:
#$> cd folder-with-pdf
#$> docker run --rm -it -v $(pwd):/docs authsec/sphinx qpdf --decrypt --replace-input my.pdf
Note
If you’re on Windows, the current working directory needs to be specified with ${PWD}.
Bulk Update
If you do have a folder full of PDFs you want to convert, open up a terminal and navigate to the folder that contains the PDFs. Next execute the following command to bulk remove the PDF write protection:
#$> cd folder-with-pdf
#$> find . -name \*.pdf -exec sh -c 'qpdf --decrypt --replace-input "{}"' \;
You can also add another command that moves the converted file into another folder like so (note that doing it as shown below will flatten your directory structure):
#$> cd folder-with-pdf
#$> find . -name \*.pdf -exec sh -c 'qpdf --decrypt --replace-input "{}"; mv "{}" ../writeProtectionRemoved' \;
If you want to combine removing write protection with Docker and reorganizing the processed file into another folder, you can combine the commands like so:
#$> cd folder-with-pdf
#$> find . -name \*.pdf -exec sh -c 'docker run --rm -it -v $(pwd):/docs authsec/sphinx qpdf --decrypt --replace-input "{}"; mv "{}" ../writeProtectionRemoved' \;
