How to unlock PDF files

Do you need to print a PDF but you cannot proceed because a warning appears on the computer screen indicating that the file is locked? Should you edit a PDF before giving it to your co-worker but you can’t because a password prevents them from being edited? I would say then that you need some “tips” on how to deal with the situation, and today I am here for this!

In the guide you are about to read, in fact, we will see together how to unlock PDF files using some of the best solutions available for Windows, macOS and Linux, usable both in the form of software and online services. In addition, I will also tell you about some apps used for the purpose for Android and iOS, so that you can also act on the go.

Then? May I know what are you still standing there? Position yourself comfortably, take a few free minutes just for you and immediately start taking advantage of the tools I am about to offer you. However, keep in mind that removing the protections from a file that you are not authorized to view, print or modify could lead to the violation of some laws. Personally, I do not take any responsibility for the misuse that you could make of the indications in this tutorial. All clear? Well, then let’s get started.

Index

• Preliminary information
• How to unlock password protected PDF files
  • QPDF (Windows / macOS / Linux)
  • PDFCrack (Windows / macOS)
• How to unlock secure PDF files online
  • iLovePDF
  • Online2PDF
• App to unlock PDF files
  • iLovePDF (Android / iOS)
  • PDF Tools (Android)

Preliminary information

Before getting into the guide, there is some information about the type of protection that can be applied to a PDF file, which is my duty to provide you.

In case you don’t know, PDF documents can be protected with a password against modification and printing or with a password against unauthorized access. In the first case, we speak of owner password, which can be removed quite easily using some software and online services available for free on the Net, while in the second case we speak of user password and the “music” is distinctly different.

The user passwords, in fact, prevent the viewing of PDF documents and cannot be removed, it is only possible to try to discover them by means of a brute force attack, i.e. letting a software try all the combinations of characters until it finds the exact keyword (process which, as easily understood, can be long and tortuous).

How to unlock password-protected PDF files

Having made the necessary clarifications above, let’s get to the action and let’s find out, therefore, how to unlock password-protected PDF files from a computer, using special programs for Windows, macOS and Linux. Find indicated those that, in my humble opinion, represent the best in the category right below.

QPDF (Windows / macOS / Linux)

The first software to unlock PDF files that I invite you to test is called QPDF. It’s free, open-source in nature, and runs on Windows, macOS, and Linux. It allows you to intervene only on the owner passwords (therefore only on the passwords for printing and modification) and works only from the command line; it is still quite simple to use.

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

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

Once the Command Prompt window on the desktop is open, enter the string qpdf –decrypt input.pdf output.pdf(in place of input.pdf and output.pdf you must type the full path of the PDF to be unlocked and the output file to be obtained) and press the Enter key on the PC keyboard. After doing this, an unlocked version of the PDF will be returned to you in the folder you indicated for the output file.

If you are using macOS, on the other hand, to download and install QPDF, you must rely on Homebrew: a free and open source package manager that allows you to install various types of software through the Terminal. So, 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.

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

When the installation is complete, type the command in the Terminal qpdf –decrypt input.pdf output.pdf(replacing  input.pdf and output.pdf you must enter the paths of the input and output files), press the Enter key on the Mac keyboard: in a few moments, you will get an unlocked version of the PDF file.

PDFCrack (Windows / macOS)

If you need to unlock a PDF file protected by a user password (therefore password against unauthorized access), the tool I recommend you to consider is called PDFCrack: it is a free and open-source software that uses brute force attacks to find the passwords of the documents in question, both on Windows and on macOS and Linux. Like the program I already told you about in the previous lines, it doesn’t have a graphical interface, it only works from the command line, but it’s not very difficult to use.

If you are using a Windows PC, you can download PDFCrack to your PC by connecting to the program website and clicking on the Download link ( pdfcrack-xx.zip, xxk) located in the right sidebar.

Next, you need to open the ZIP archive that contains PDFCrack, extract its contents to a folder of your choice and open a Command Prompt window, holding the Shift key on your keyboard, right clicking on the folder where you extracted PDFCrack and selecting the voice  Open command window here from the menu that appears.

Now that you see the Command Prompt window on the screen, type the command pdf crack “file.pdf”(instead of file.pdf you have to enter the path and name of the PDF to be unlocked) and hit the Enter key on your PC keyboard.

Afterwards, the password search process for the selected document will start. At the end of the procedure, you will be shown the message found user-password, followed by the password to open the PDF.

If you use macOS, however, you can download PDFCrack by connecting to this web page on the SourceForge website and clicking on the Download Latest Version button located at the top.

When the download is complete, open the tar.gz archive you just downloaded, extract the contents in any folder and open the Terminal, selecting the icon (the one with the black window and the line of code ) that you find in the Other folder of the Launchpad.

At this point, issue the command cd \[percorso in cui hai estratto PDFCrack] (instead of [percorso in cui hai estratto 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 [percorso in cui hai estratto PDFCrack]/pdfcrack -u [file PDF da sbloccare] (instead of [percorso in cui hai estratto PDFCrack]you must enter the full path of the folder where you extracted PDFCrack and instead of [file PDF da sbloccare]you must enter the full path and name of the file to be decrypted ) and hit the Enter key again .

Subsequently, the search for the password necessary to open the selected PDF file will start, at the end of which the message found user-password will appear , followed by the keyword found by the program.

How to unlock secure PDF files online

If you do not want or cannot download new programs on your computer, I inform you that it is possible to unlock a secure PDF file online, using the appropriate Web services. If you are interested in this, read on. In fact, in the following steps you will find described those which, in my humble opinion, constitute the most interesting tools of this type.

iLovePDF

If you need to remove the password from a PDF protected against printing or modification (we are therefore talking about owner password), you can take advantage of iLovePDF: an online service that does not require registration and that supports uploading files up to 200 MB. It’s free, but you can possibly subscribe to one of the paid plans (starting from 6 euros/month) to access extra features, such as increasing the maximum file upload size to 1 GB. It should be emphasized, then, how the service protects the privacy of users by automatically deleting the files that are uploaded to its servers within a few hours after the upload.

To use iLovePDF, connect to the service’s website and drag the document you want to work on into the browser window; alternatively, select the file “manually” by clicking on the Select PDF file button. You can also get the file from Dropbox or Google Drive by clicking on the relevant icons and logging into your account.

To conclude, click on the Unblock PDF button, located at the bottom right, wait a few moments for the procedure to be completed and wait for the download of the unlocked document to start automatically. Otherwise, click on the Download unlocked PDFs button to force the download. You can also choose to save the final file on Dropbox or Google Drive or share the link by clicking on the appropriate buttons on the right.

Online2PDF

Online2PDF is another free, registration-free online service useful for editing, converting and unlocking PDF files. It allows you to act both on files protected against printing and modification and on files protected against unauthorized access, but in the latter case you need to know the password of the document in order to create a “free” copy. It should also be noted that it has some restrictions regarding upload: you cannot upload more than 20 files at a time and these must have a total weight not exceeding 100 MB. Regarding the protection of users’ privacy, Online2PDF deletes the files that are uploaded to its servers within a few hours.

To use Online2PDF, linked to its home page and drag the documents to be unlocked on the Select files button, in order to upload them. Alternatively, click on the button in question and “manually” select the documents you intend to act on.

After upload, if you are trying to unlock a PDF protected from unauthorized access, click on the black button with the padlock that appears next to the document name, type the password used to protect the PDF in the dedicated field and click on the Convert button that is located at the bottom, in order to download an unlocked copy of the document.

If, before proceeding with the download of the document, you wish to intervene on the degree of compression, on the display, on the header and footer or on the layout, you can do so by selecting the appropriate tabs at the bottom, in the Preferences section , and acting on the items and menus that appear. If, on the other hand, you need to rotate the pages, select them, reorder them or divide them, first click on the button with the page and/or the one with the phobics, which you find next to the name of the document.

App to unlock PDF files

To conclude, I would like to point out some apps to unlock PDF files that you can use on Android smartphones and tablets and on iOS devices, to perform the operation in question on the go.

iLovePDF (Android / iOS)

iLovePDF, the web service I mentioned in the previous lines and through which it is possible to unlock PDFs protected by owner password, is also usable in the form of an app for Android and iOS devices. It is free, but offers in-app purchases to subscribe to a subscription (at a cost of € 5.99 / month or € 48.99 / year) that allows you to remove advertisements and take advantage of other extra features.

To download the app on your Android device, 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 iLovePDF is displayed, tap the Unlock button, choose whether to take the PDF from the device, from Google Drive or from Dropbox and select the document of your interest.

Then, click on the Unblock PDF button located at the bottom and wait for the unlocking process to be completed. Then when you see the word Completed! on the screen, press the Go to file button to access the unlocked version of the PDF.

PDF Tools (Android)

If you are using an Android-based device, you can also evaluate the use of the free PDF Tools app, which allows you to rotate, split and merge PDFs and perform various other operations on the type of file in question. Among the various things it allows you to do, the app also offers the ability to remove the password that blocks PDFs from editing and printing. In this case, however, it is necessary to know the password to unlock the document, in order to create a freely accessible copy.

To download it to your device, visit the relevant section of the Play Store and tap the Install button. Then, start the app by pressing the Open button that appeared on the screen or select the relative icon that has just been added to the drawer.

Once the main screen of the app is displayed, choose whether or not to receive personalized ads (I recommend not), press the OK button, tap the Accept and continue button, to accept the terms of use, and allow PDF Tools to access photos, media and files on your device.

Next, hit the button Unlock PDF, tap the Select PDF Files button and select the PDF you want to act on. Therefore, type the password used to protect the PDF in the appropriate field and press the checkmark located at the bottom right.

Afterwards, you will be returned an unsecured copy of the previously selected document, saved in the same location as the original one.