Index
- Preliminary information
- How to unlock a secure PDF
- How to unblock a PDF online
- App to unlock PDF
- iLovePDF (Android / iOS / iPadOS)
- PDF Tools (Android)
Preliminary information
Before going into the reading of this guide, then going to find out how to unlock a PDF, there is some preliminary information that it is my duty to provide you, to make sure that you have perfectly clear ideas on the matter and that everything goes in the right way.
To begin with, keep in mind that to unlock a PDF with a password it is first of all essential to understand what type of protection has been set on the document in question. In fact, PDFs can be protected with two different types of passwords: the owner password, which does not allow printing and editing of the file, and the user password, which instead prohibits its opening.
Understanding the difference above is essential to be able to identify the most suitable tool to unlock the PDF of your interest. There are, in fact, many tools suitable for the purpose, but these are hardly able to simultaneously unlock the owner password and user password, which have a totally different level of vulnerability.
Going into more detail, the owner password can usually be bypassed in a few moments, while the user password can only be found using the brutal forcing, which consists of trying all possible combinations of characters until the correct secret word is found, which could take several hours or even days, putting a strain on the computer's CPU.
How to unlock a secure PDF
Having made the necessary clarifications above, let's get to the heart of the matter and let's find out, first of all, what are the software which can be used to unlock a secure PDF by acting as a computer. You can find them indicated below. There are both for Windows that for MacOS e Linux.
QPDF (Windows / macOS / Linux)
The first PDF unlocking tool I recommend you put to the test is QPDF. It is a free, open source program that can be used on Windows, macOS and Linux, which allows you to bypass the protection applied to the files belonging to the category covered by this tutorial, by intervening on the owner password. Note that it does not have a graphical interface, so it can only be used from the command line.
To download the program to your PC, if you are using Windows, go to the QPDF download page on the SourceForge website and click on the button Download Latest Version at the top left.
Once the download is complete, extract theZIP archive obtained and start QPDF using the Command Prompt, directing it to the folder that contains the program. If you don't know how to do this, just hold down the button Shift on your computer keyboard, right click on the folder bin present in the folder where you extracted QPDF and, from the menu that appears, select the item Open command window here.
Now that you see the Command Prompt window on the screen, enter the following string: qpdf --decrypt input.pdf output.pdf (instead of input.pdf and output.pdf you have to enter the full path of the PDF to be unlocked and the file output to get; you can get the full path of a file by dragging it to the command line) and press the key Submit. After that, you will get an unlocked version of the PDF in the folder chosen for the output file.
Instead, if you are using MacOS, to download and install the program you have to take advantage of Homebrew, a free and open source package manager that allows you to install various software using the terminal. So, first of all, open the latter by clicking on the icon Launchpad (Quella with il space rocket) that you find on Dock barby selecting the folder Other and then clicking onTerminal icon (Quella with the nether finest in the riga di codice).
Now that you see the Terminal window on your desktop, to install Homebrew type the following string: / usr / bin / ruby -e "$ (curl -fsSL https://raw.githubusercontent.com/Homebrew/install/master/install) ", then press the key Submit on your Mac keyboard and, when prompted, enter the administration password Of computer. Next, install QPDF by entering the string brew install qpdf, always followed by pressing the key Submit.
Once the installation procedure is complete, enter the command qpdf --decrypt input.pdf output.pdf in the Terminal window (instead of input.pdf and output.pdf you must type the paths of the input and output files; you can obtain the complete with a file by dragging it to the command line), press the key Submit and an unlocked version of the document will be returned to you.
PDFCrack (Windows / macOS)
Another tool you can consider testing to unlock PDFs is PDFCrack. It allows you to act on files protected from opening, therefore on those for which the user password has been set, works on both Windows and macOS and is also usable from the command line, as it does not have a graphical interface.
Stai using Windows, to download it, go to the relevant website and click on the link Download(pdfcrack-xx.zip, xxk) located on the right.
Once the download is complete, extract the contents of theZIP archive just got into a folder of your choice. Then click on the Start button (I cheer with the windows flag) che trovi nella part in fund to sinistra della taskbar), type prompt in the search field displayed on the screen and select the collegamento related to Command Prompt give the menu to compare.
In the window that you now see on the screen, enter the following string: CD "[PDFCrack folder]" (instead of [PDFCrack folder] you have to type the entire path of the folder where you extracted PDFCrack) and press the key Submit on the PC keyboard. Then insert the string pdfcrack "file.pdf" (instead of file.pdf you have to type the complete path and the name of the file to be decrypted) and press the key again Submit.
After completing the above steps, PDFCrack will begin to "attack" the PDF to find the password. When it finds it, you will see the message found user-password, followed by the passkey to unlock your file.
Se, invece, stai using MacOS, to download PDFCrack you have to visit the download page on the SourceForge website and click on the button Download Latest Version located at the top.
Once the download is complete, open thetar.gz archive obtained and extract the contents into a folder of your choice. Afterwards, call up the terminal, selecting theicon (Quella with the nether finest in the riga di codice) found in the folder Other of Launchpad.
At this point, type the command cd [PDFCrack folder] (instead of [PDFCrack folder] you must enter the full path of the folder where you extracted PDFCrack) and press the key Submit on the keyboard. Next, also enter the string make f Makefile, always followed by pressing the key Submit.
Once all the above steps have been completed, open a new Terminal window, enter the command [PDFCrack folder] / pdfcrack -u "file.pdf" (instead of [PDFCrack folder] you have to type the complete path of the folder in which you have extracted PDFCrack and instead of file.pdf you have to enter the full path and name of the file to be decrypted), press the key again Submit and you can finally find out the password to unlock your PDF.
How to unblock a PDF online
You don't want or can't download new programs to your computer, and you'd like to know if there are any tools you can use to unlock a PDF by taking action online? Of course yes, God forbid! In fact, below you will find those that, in my humble opinion, represent the best solutions of this type. Try them now!
Online2PDF
Online2PDF is an online service running from any browser and operating system and usable without registration, which allows you to unlock PDFs protected from printing and modification (owner password), but also those protected from unauthorized access (user password), provided, in in the second case, to know the relative password in order to generate a "free" version of the document. Note that the tool also allows you to edit and convert PDFs, even by acting on multiple files in sequence.
The service is free, but it allows you to upload no more than 20 files at a time. Furthermore, it should be noted that the maximum size allowed for individual files is 100 MB and that the total size must not exceed 150 MB. As for the privacy issue, Online2PDF removes the files uploaded to its servers within a few hours of uploading.
To use Online2PDF, go to the home page of the service and drag the PDFs in relation to which you are interested to intervene on the dotted rectangle located in the center. If you prefer to upload the files "manually", click on the button Select files and select the PDFs of your interest.
Once the upload is complete, if you want to unlock PDFs protected with an owner password, click on the button directly Converted, below, and waits for a “free” copy of the files to be created and their download to start automatically. If the download does not start automatically, you can force it by clicking on the link Switch to manual download that is shown to you.
Do you want to unlock PDF protected with user password? In this case, before proceeding with the download as I have indicated above, you will have to click on the black button with the padlock that you see appear in correspondence with the name of each document after the upload and enter the relative access key in the field provided.
iLovePDF
Another web service you can consider using to unlock a PDF is iLovePDF. It too does not require registration and works from any browser and operating system. It allows you to unlock PDFs protected by owner password and user password, but in this second case it first requires the entry of the relative access key, so as to be able to create a freely accessible copy. In addition to the purpose in question, the service can also be used to convert PDFs, split them, merge them etc.
Note that this is a free solution, but it does not allow you to upload files with a weight greater than 100 MB. If you want to get around this limitation, you need to switch to one of the paid plans (with costs starting from 6 euros / month), which allow you to upload files with a maximum weight of 1 GB and to unlock other extra features. As for the issue of privacy protection, the service removes the files that are uploaded to its servers within a few hours.
In order to use iLovePDF, the first step you need to take is to visit its home page and drag the PDF to be unlocked into the browser window. If you prefer to select the file "manually" instead, click the button Select PDF file and download the PDF from your computer. You can choose to upload the document from your account as well Google Drive o dropboxby clicking on the appropriate buttons.
Once the upload procedure is complete, click on the button Unlock PDF which is shown to you at the bottom right. After that, the download procedure of the unlocked file will start automatically. If not, force the download by clicking the button Download the unlocked PDFs. You can also decide to save the final file to Google Drive, its dropbox or you can choose to share theURLby pressing the appropriate buttons on the right.
Keep in mind that if the PDF you have chosen to unlock is protected by a user password, before you can proceed with the download, you must also type the password of the file in the appropriate field that you will see appear on the screen and click on the button Send.
App to unlock PDF
Now I want to point out the ones that, in my opinion, represent the best app to unlock PDF from smartphones and tablets. You will find them indicated below.
iLovePDF (Android / iOS / iPadOS)
iLovePDF, the service I told you about in the step at the beginning of the guide, is also available as an app for Android and iOS / iPadOS. It resumes in all respects the functioning of the Web variant, thus allowing you to intervene both on PDFs protected with an owner password and with a user password, but in this second case you must first type in the relative secret word (in order to be able to create a copy of the unlocked document). Note that the app is free, but offers in-app purchases to subscribe to the paid service plan (at a cost of € 5,99 / month or € 48,99 / year), to remove advertising and benefit from other extra features.
To download the app on Android, visit the relative section of the Play Store and click on the button Install. If, on the other hand, you are using iOS / iPadOS, access the relevant section of the App Store, tap the button Get, then that Install and authorize the download via Face ID, touch ID o password dell'ID Apple. Then, start the app by pressing the button apri comparso sul display oppure selecting the relative icon which has been added to the home screen.
Now that you see the main screen of the app, click on the button Unlock, decide whether to get the PDF from the device or from one of the cloud storage service supported (Google Drive or Dropbox) and select the file of your interest.
Finally, click on the button Unlock PDF that is shown to you below and, when you see the writing appear Completed! on the display, you can proceed with the download of the output document by pressing the button Go to file, to access the unlocked version of your PDF.
Keep in mind that if the PDF you want to unlock is protected by a user password, before proceeding with the download as I have just indicated, you will be asked to type the relative password in the appropriate field.
PDF Tools (Android)
As an alternative to the app I have already told you about, if you are using a smartphone or tablet Android, you can contact PDF Tools. It is free and offers a series of useful tools to intervene on PDFs in various ways: by merging them, dividing them, removing some of the pages that compose them, etc. I chose to tell you about it as it also allows you to unlock PDFs protected by owner password and user password, requiring, in this second case, first the entry of the relative secret word, in order to be able to create a free copy.
To download and install the app on your device, visit the relevant section of the Play Store and tap the button Install. Then start the app by pressing the button apri comparso sullo schermo oppure selecting the relative icon which has just been added to the drawer.
Now that you see the main screen of the application, choose whether or not to receive personalized ads (I recommend not), press the button OK and accept the terms of use by tapping the button Accept and continue. Then allow PDF Tools to access photos, media and files on your device.
After completing the above steps, click on the button Unlock PDF, tap the button Select PDF Files and select the PDF of your interest saved on the memory of your device. If the PDF you have selected is protected with a user password, also enter the password applied to it in the field provided.
Finally, select the checkmark appeared at the bottom right and you can download the unlocked document, which will be saved in the same location as the original file. Easier than that?
How to unlock a PDF
