How to unprotect PDF files

Index

• Preliminary information
• How to unprotect protected PDF files
  • QPDF (Windows / macOS / Linux)
  • PDFCrack (Windows / macOS)
• How to unprotect a PDF file online
  • PDF Candy
• App to unprotect PDF files
  • iLovePDF (Android / iOS)
  • PDF Utility (Android)

Preliminary information

Before getting to the heart of the tutorial, let's find out what the tools are available for unprotect a PDF file and how to use them, it is my duty to do some precision to about.

PDF documents can be protected by a password that prevents them from being opened, printed or modified by unauthorized users. In the first case, the one that prevents the document from being displayed, we are talking about user password. When, on the other hand, the password only blocks the printing, selection or modification of text, it is called owner password.

It is important to know this difference, as there are applications and online services that allow you to remove the protection from PDF files, but they hardly deal with both types of passwords, also because their degree of vulnerability is very different.

The owner password can often be bypassed in a few moments, while the user password is much more difficult and can only be discovered with the "brute forcing" technique, ie by trying all possible combinations of characters until the right one is found . This operation can take several hours, if not entire days.

How to unprotect protected PDF files

Having made the necessary clarifications above, let's get to the point and let's find out how to unprotect a protected PDF file from a computer, using special software: below you will find those that I believe to be the best in the category.

QPDF (Windows / macOS / Linux)

The first of the useful tools to unprotect a PDF file on a computer, which I recommend you to test, is QPDF: it is a free, open source and compatible tool not only with Windows, but also with macOS and Linux. Allows you to work only on PDFs that are protected from printing and editing. It is very effective but, unfortunately, it does not have a graphical interface and must be used from the command line (nothing very complicated though, I promise!).

To download the program on Windows, then visit the download page on the SourceForge website and click on the button Download Latest Version, which is located at the top left.

Once the download is complete, extract theZIP archive obtained in a folder of your choice and start QPDF using the Command Prompt, directing it directly to the folder that contains the program. If you don't know how to do this, press and hold the key Shift on the keyboard, right click on the folder bin located in the folder where you extracted QPDF and select the item Open command window here give the menu that comes mostrato.

Once the Command Prompt window appears, enter the string qpdf --decrypt input.pdf output.pdf (instead of input.pdf e output.pdf you have to type the full paths of the PDF to unlock and of the output file to get) and press the key Submit on the keyboard. Once these steps have been completed, you will get an unlocked version of the PDF in the folder intended for the output file.

Stai using MacOS, to download and install the program you have to rely on Homebrew, an open source, no-cost package manager that allows you to install various types of software via the terminal. That said, first of all open the terminalby selecting the relevant icon (Quella with the nether finest in the riga di codice) present in the folder Other of Launchpad.

Once the Terminal window is displayed, to install Homebrew, enter the command / usr / bin / ruby ​​-e "$ (curl -fsSL https://raw.githubusercontent.com/Homebrew/install/master/install)", then press the button Submit on the keyboard and type the Password Mac administration. Once this is done, proceed with the installation of QPDF, issuing the command `brew install qpdf, always followed by pressing the Submit.

Once the installation procedure is complete, type the command qpdf --decrypt input.pdf output.pdf (instead of input.pdf e output.pdf you have to enter the paths of the input and output files) and you will get an unlocked version of your PDF file.

PDFCrack (Windows / macOS)

Another good tool you can rely on to remove the password from your PDF files is PDFCrack: it is a free and open source software, available for Windows and macOS, which allows you to unprotect user password protected PDF files using the brute force technique, i.e. trying to unlock the file using all possible combinations of characters. Also in this case, we are in the presence of a tool that does not have a graphical interface and must be used from the command line. In any case, fear not, it is not difficult to use.

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

Once the download is complete, open theZIP archive obtained, extract the contents into a folder of your choice and start the Command Prompt, facendo click sul Start button (I cheer with the windows flag) che trovi nella part in fund to sinistra della taskbartyping "Prompt" in the search field and selecting the relevant colleague from the list shown.

Now that the Command Prompt window is displayed on the desktop, issue the command CD "[PDFCrack folder]" (instead of [PDFCrack folder] you have to enter the full path of the folder where you extracted PDFCrack) and press the key Submit on the keyboard. Next, enter the pdfcrack command "file.pdf" (in place of file.pdf, you must enter the complete path and the name of the file to be decrypted), always pressing the key Submit later.

When processing is complete, the message will appear on the Command Prompt screen found user-password, followed by the password to unlock the selected PDF.

If, on the other hand, you want to download PDFCrack for MacOS, visit the page dedicated to the program on the SourceForge website and click on the button Download Latest Version, located at the top.

Once the download is complete, open the archive tar.gz obtained and extract the contents to any folder. Next, launch the terminalby selecting the relevant icon (Quella with the nether finest in the riga di codice) found in the folder Other of Launchpad, issue the command cd [PDFCrack folder] (instead of [PDFCrack folder] you have to enter the full path of the folder where you extracted PDFCrack) and press the button Submit on the keyboard. Once this is done, enter the make -f Makefile command, always followed by pressing the key Submit.

At the end of the compilation of the program, close the Terminal, reopen it and give the command [PDFCrack folder] / pdfcrack -u "file.pdf" (instead of [PDFCrack folder], you must enter the full path of the folder where you extracted PDFCrack, while in place of file.pdf you have to enter the full path and the name of the file to decrypt), then press the key Submit on the keyboard, in such a way as to start the password search for your PDF which, if all goes well, you will be able to view on the screen after some time.

How to unprotect a PDF file online

As I told you at the beginning of the guide, it is also possible sprotegere a PDF file online resorting to the use of some special Web services, functioning without the slightest problem from any browser and operating system. If you are interested in this, I have listed the most interesting ones below.

PDF Candy

A great online service that you can consider using to unprotect a PDF file is PDF Candy: it is a resource through which it is possible to perform various types of operations on the documents in question, which is easy to use and does not require payments to access extra features. It does not set limits for what concerns the upload of files and, moreover, it protects the privacy of users by eliminating what is uploaded to its servers within a few hours. Note, however, that in the case of PDF unblocking, you need to know the key word, in order to obtain a "free" version of the document.

To use PDF Candy, visit the home page of the service and drag the file of your interest to it. If you prefer to select it "manually", click the button first Add files. If, on the other hand, your document is on Google Drive o dropbox, you can upload it from there, by clicking on the icon relating to the service of your interest.

Once uploaded, type the password to unlock the PDF in the field Password present at the bottom, then click on the button first Unlock PDF e poi quello Download file, to download the unlocked version of the document. If you prefer to archive the file on Google Drive or on dropbox, select the relevant ones icon And that's it.

App to unprotect PDF files

Finally, let's move on to app per sprotteggere in file PDF from smartphones and tablets, without necessarily having to go to the computer: below are listed those that, in my opinion, you would do well to take into consideration.

iLovePDF (Android / iOS)

iLovePDF is an excellent free application, available for both Android and iOS, thanks to which it is possible to perform various operations on selected PDFs. The documents, in fact, can be converted into other formats, modified, divided etc. Of course, it is also possible to unprotect owner password protected PDFs, all in a handful of taps. It is free, but offers in-app purchases to subscribe to the paid plan of the service (at a cost of 5,99 euros / month or 48,99 euros / year), which allows you to remove advertising and take advantage of additional features .

To download the app on Android, visit the relative section of the Play Store and press the button Install. If, on the other hand, you are using iOS, access the relevant section of the App Store, press the button Get, quindi quello Install and authorize the download via Face ID, touch ID o Password Apple ID. Then, start the app by pressing the button apri comparso sullo schermo oppure selecting the relative icon which has just been added to the home screen.

Ora che visualizzi la schermata principale dell'app, fai tap sul pulsating Unlock, indicates whether to get the protected PDF from device, from Google Drive or from dropbox and select il document to unlock. Then click on the button Unlock PDF appeared at the bottom, wait for the unlocking process to be completed and, when you see the writing appear Completed! on the display, press the button Go to file, to access the passwordless version of the document.

PDF Utility (Android)

If you are using a device Android, you can also evaluate the use of the app PDF Utility, for unlocking PDFs: it is a free tool, easy to use and through which it is possible to intervene in various ways on PDFs and unlock those protected by owner password. In fact, it allows you to create an unlocked copy of PDFs, provided you know the password with which they are protected. It should be noted that it is possibly available in a paid version (at a cost of 2,79 euros), which allows you to bypass the 2,5 MB limit for uploading documents established for the free version and allows you to access other extra features.

To download the app on your device, visit the relevant section on the Play Store and press the button Install. Afterwards, launch PDF Utility by touching the button apri comparso sul display oppure selecting the relative icon which has just been added to the home screen.

Now that you see the app home screen, select the icon Unlock PDF, award your bottone Select File and select il PDF concerning which you are interested in going to act. Therefore, type the Password used to protect the document in the field File owner password and his bottone award Decrypt File.

When the procedure is complete, you will be shown a specific message on the screen. At that point, you can choose whether to open the unlocked document obtained (by tapping on the item Open) or whether to share it (by pressing on the item Share). That's all!

How to unprotect PDF files