How to unlock secure PDF

Have you downloaded a PDF file from the Internet but can’t print it because you’re being asked to type in a password you don’t know? Have you recovered some PDF documents from an old USB stick but you can’t open them because you don’t remember the password needed to view the contents? Maybe I can help you out.

I know some solutions for Windows and macOS that allow you to unlock a secure PDF  quite easily. I think they are right for you! How do you say? Would you like to know if there is also some resource that can be used directly from the browser window or from the screen of your smartphone or tablet? Yes, of course! In the following chapters, in fact, you will also find online services and apps that can be useful in this sense.

But now just chat and let’s take action. Make yourself comfortable, take a few minutes of free time just for you and start concentrating on reading what is written below. Whichever tool you choose to use, you should be successful. However, keep in mind that bypassing the protection of PDFs that you are not the legitimate owner of (or in any case without having permission) can be a crime. Therefore, I do not take any responsibility for the use you will make of it. Clear? Well then let’s get started!

Index

• Preliminary information
• How to unlock secure PDF for free
  • QPDF (Windows / macOS / Linux)
  • PDFCrack (Windows / macOS)
• How to unlock secure PDF online
  • Online2PDF
• App to unlock secure PDF
  • iLovePDF (Android / iOS)
  • PDF Utilities (Android)

Preliminary information

Before getting to the heart of the tutorial, going to explain how to unlock a protected PDF, there is some preliminary information, in this regard, that it is my duty to provide you.

You need to know that passwords applied to PDFs are not all the same. The type of file in question, in fact, can be protected with two different types of passwords: one is the owner password, which prevents you from making changes or printing the documents and is very easy to remove; the other is the user password which, on the other hand, totally prevents access to the files and can only be discovered through a brute-force attack, that is, by trying all possible combinations of characters, and this operation can take a very long time.

How to unlock secure PDF for free

Having made the above clarifications, let’s get to the point and let’s find out, in detail, how to unlock a protected PDF using some programs for Windows,  macOS and Linux: the ones I will talk about in the following steps. They are completely free tools and, while on the surface it may seem the opposite, they are also quite simple to use.

QPDF (Windows / macOS / Linux)

The program that I recommend you to use to remove the owner password, that is the password against printing or document changes, is  QPDF. It’s free, open-source, and available for Windows, macOS, and Linux. It works from the command line, does not have a graphical interface, but is equally simple to use.

To download the program on Windows, go to the QPDF download page on the SourceForge website and click on the Download Latest Version button, located at the top left.

Once the download is complete, extract the ZIP archive obtained in a folder of your choice and start QPDF via the Command Prompt, directing it directly to the folder containing the program. If you don’t know how to do it, proceed as follows: hold down the Shift key on your keyboard, right-click on the bin folder in the folder where you extracted QPDF and select the Open command window here item from the menu that is shown to you.

Once the Command Prompt window appears on the screen, type the string qpdf –decrypt input.pdf output.pdf(instead of input.pdf and output.pdf you have to type the full path of the PDF to be unlocked and the output file to be obtained, you can get the full path of a file by simply dragging it to the line of command) and press the Enter key on your keyboard. After following these steps, you will get an unlocked version of the PDF in the folder you indicated for the output file.

If you are using macOS, to download and install QPDF, you must instead rely on Homebrew, a free and open-source package manager that allows you to install various types of software using the Terminal. Having said that, first of all open the Terminal, selecting the relative icon (the one with the black window and the line of code ) that you find in the Other folder of the Launchpad.

Once the Terminal window is displayed on the desktop, to install Homebrew, enter the command /usr/bin/ruby -e “$(curl -fsSL https://raw.githubusercontent.com/Homebrew/install/master/install)”, followed by pressing the Enter key on the keyboard and entering the Mac administration password. Then, to install QPDF, type the command brew install qpdf, always followed by pressing the Enter key.

Once the installation procedure is complete, enter the command in the Terminal qpdf –decrypt input.pdf output.pdf(instead of input.pdf and output.pdf you have to type the paths of the input and output files, I remind you that even in this case you can get the full path of a file simply by dragging it to the command line) , hit the Enter key on your Mac keyboard and you will get an unlocked version of the PDF document.

PDFCrack (Windows / macOS)

If your need is to unlock a PDF protected by a user password, I suggest you rely on  PDFCrack: it is a free and open-source program, available for Windows and macOS, which uses the system of brute-force attacks to make documents accessible. Even in this case, however, it is a resource that works exclusively from the command line.

To download it on Windows, visit the program website and click on the Download link ( pdfcrack-xx.zip, xxk) located in the right sidebar.

Once the download is complete, open the ZIP archive obtained, extract the contents into a folder of your choice and call up the Command Prompt, by clicking on the Start button (the one with the Windows flag ) located at the bottom left of the taskbar, by typing “prompt” in the displayed search field and selecting the relevant link from the menu.

Now that you see the Command Prompt window on the screen, enter the command CD “[cartella PDFCrack]”(instead of [cartella PDFCrack]you have to enter the full path to the folder where you extracted PDFCrack) followed by pressing the Enter key on your keyboard. Then type the command pdf crack “file.pdf”(instead of file.pdf you must enter the full path and the name of the file to be decrypted), always pressing the Enter key.

After completing the above steps, PDFCrack will start attacking the document to find its password. When found, you will be shown found user-password, together with the password needed to open the file.

If you are using macOS, on the other hand, to use the program visit the page dedicated to it on the SourceForge website and click on the Download Latest Version button located at the top.

When the download is complete, open the tar.gz archive obtained and extract the contents in a folder of your choice. Next, call the Terminal, selecting its icon (the one with the black window and the line of code ) that you find in the Other folder of the Launchpad and issue the command cd [cartella PDFCrack](instead of [cartella PDFCrack]you must enter the full path of the folder where you extracted PDFCrack) , followed by pressing the Enter key on the keyboard. Then type the command make f Makefile, always followed by pressing the Enter key.

After carrying out the steps in question, open a new Terminal window, type the command [cartella PDFCrack]/pdf crack -u “file.pdf”(instead of [cartella PDFCrack]you must enter the full path of the folder where you extracted PDFCrack and instead of file.pdf you must enter the full path and name of the file to be decrypted ), press the Enter key on your keyboard and you will finally be able to view the document password.

How to unlock secure PDF online

If you do not want to download programs on your computer, I inform you that, to unlock a protected PDF, you can also intervene online, using special Web services, such as those I will talk about in the following steps, which are functional from any browser and operating system.

Online2PDF

Online2PDF is an online service dedicated exclusively to editing, converting and unlocking PDFs. In the latter case, if it is a user password, you need to know the password of the PDF in order to create a “free” copy. It should also be noted that it has restrictions on uploading. The service, in fact, does not allow you to upload more than 20 files at a time, which must have a total weight not exceeding 100 MB. Regarding privacy, Online2PDF removes files uploaded to its servers after processing.

To use the service, go to its home page, click on the Select files button and select the documents to be processed. Alternatively, drag and drop files directly into the browser window. After upload, if you need to unlock a file protected from unauthorized access, click on the black button with the padlock that you see appearing next to the document name, type the password used to protect the PDF in the appropriate field that is shown to you and click on the button Convert below to download an unlocked copy of the document.

If before downloading the document you want to intervene on the degree of compression, on the display, on the header and footer or on the layout, I inform you that you can do it by selecting the appropriate tabs located at the bottom, in the Preferences section, and acting on the various items and on the various menus that appear. If, on the other hand, you want to rotate the pages, select them, reorder them or split the file, click in advance on the button with the page and/or on the one with the phobics that you find next to the name of the document.

App to unlock secure PDF

To conclude, I want to tell you about some apps that you can use on Android and iOS to unlock a secure PDF on the go. Put them to the test now, I’m sure they will satisfy you!

iLovePDF (Android / iOS)

The first of the apps useful for unlocking a PDF that I invite you to consider is iLovePDF: it is a free solution, available for Android and iOS, which, separately unlocking PDFs (allows you to remove only the owner password) , allows you to perform various types of operations on the type of file in question. It is free, but offers in-app purchases to subscribe to the paid plan of the service (at a cost of € 5.99 / month or € 48.99 / year), which allows you to remove advertisements and take advantage of other features extra.

To download the app on Android, visit the relevant section of the Play Store and tap the Install button. If, on the other hand, you are using iOS, access the relevant section of the App Store, tap the Get button, then the Install button and authorize the download via Face ID, Touch ID or Apple ID password. Then, start the app by pressing the Open button that appeared on the display or by selecting the relative icon that has been added to the home screen.

Once the main screen of the app is displayed, press the Unlock button, decide whether to take the PDF from the device, from Google Drive or from Dropbox and select the document of your interest.

Then, tap on the Unlock PDF button that appeared at the bottom and wait for the unlocking process to start and complete. When you see the word Completed! on the display, you can press the Go to file button to access the unlocked version of your PDF. Easier than that?

PDF Utilities (Android)

Another app you can rely on to unlock owner password-protected PDFs is  PDF Utilities for Android. It is free, very simple to use and, in addition to fulfilling the purpose in question, it also allows you to edit documents by removing and adding pages.

To download the application on your device, visit the relevant section on the Play Store and tap the Install button. Then, start PDF Utilities by touching the Open button that appeared on the display or by selecting the relative icon added to the home screen.

Once the main application screen is displayed, press the button with the three horizontal lines located at the top left and, from the menu that opens, select the Remove write-protection option. Then press the Select button, grant the app the necessary permissions to access the files on your device and select the PDF you are interested in going to act.

Then, press the Start button and wait for the app to process the document. When the process is complete, a new unprotected file will be generated, which will be automatically saved in the same location as the original one.