PDF is an amazing format for various reasons. It can contain both images and rich text. Also, one can not alter a PDF, without leaving a digital footprint. And the best part is, password protecting PDF is platform independent, i.e. if you encrypt a PDF using a Windows program, the recipient can still decrypt it on a different platform like MAC, Android or even on email. You don’t need the same software on both sides. There are two types of password protection on PDF — owner password and user password. The owner password is needed if you want to change permission settings like copying or printing a PDF. And the open password is used to open the PDF file. Now, if you ask me, there is no point of setting an owner password since it can be easily bypass. For instance, if the user can see the document, they can also easily copy or print it by taking its screenshot and using a good OCR reader. So, here, we’ll focus only on user password or the password required to open a PDF file. So let’s get started.
Password Protect PDF
Windows
The most popular program to encrypt PDF in Windows is Adobe Acrobat. But, if you only want to password protect few PDF, there is no need to spend money on Adobe Acrobat. A free program like pPDFmate can do the same thing for you.
Simply download and install this program like you do with any other Windows application. Then open the pdf in it, that you want to encrypt. Select the file > security > open password > assign a strong password > click build.
macOS
Encrypting a PDF is very simple in macOS. You can use the built-in Preview for that. Simply open the PDF file with MAC’s preview. Click on the ‘File’ tab on the menu bar and click on ‘Export’.
Check the box before ‘Encrypt’ and you’ll see a password space that pops-up right under. Choose an alpha-numeric password and click on ‘Save’ to save your new file with 128-bit RC4 encryption. Your old file will not be affected with this step and only the new file gets the password protection.
Android
It’s strange that Adobe Acrobat’s Android app, do not have any option to protect a PDF. But you can use other free apps like PDF Utility. Start by downloading the app from Google Play. Next, open it > password protection > import the PDF from your device memory. If you don’t see any directory, clear the app data and try again.
Now, you’ll see two password option — owner password and user password. As explained at the beginning of this article, the owner password is for permission and user password is what we need to open the document. To avoid confusion enter the same password on both and save changes. And that’s it.
iOS
Sadly there is no free way to encrypt PDF in iOS. And that’s not a surprise to me; most good iOS apps are paid anyway. But, if you are ready to spend some cash, try Pages from Apple. For $10 you get lots of options including password protecting a PDF file. But if you want to do it free, then you can still do it by using online service.
Online Service
There are many online tools that password protect a PDF. I prefer PDFprotector for two reasons. One they use https and second, as per their privacy policies they do not read/store your PDF on their server
The good thing about these online services is that they are free and platform independent. But as they say, there is no free lunch; this also comes with some risk. Like, you are uploading your confidential data to a third party server, and if they want they can see all its content. And this why, I prefer the desktop app over online tools.
Closing words
So here we have seen different ways to encrypt a PDF file. Though remember, PDFs are not very secure, it’s relatively easy to decrypt PDF with simple brute force attacks, so make sure to choose a strong password and not some dictionary words.
