How To Encrypt A PDF

In this tutorial we will look at how to encrypt and decrypt PDF’s using one of my favourite free PDF editors, PDFill. It’s free for commercial and non-commercial uses. This is Windows only software and is supported by the following operating systems:

  • Windows 2000 (32 and 64 bit)
  • Windows XP (32 and 64 bit)
  • Windows 2003 (32 and 64 bit)
  • Windows 2008 (32 and 64 bit)
  • Vista (32 and 64 bit)
  • Windows 7 (32 and 64 bit)

Java is also required to already have been installed on the machine. You can check here to see if you have Java.

Firstly, download and install the program which you can download here. Once you have started the program, you will see the main screen with multiple options.


Main window

As we are wanting to encrypt a PDF so that it can be safely sent to a client or hosted online somewhere for download, we will select No.3 Encrypt and Decrypt Options.

choose pdf

Navigate to the PDF that you wish to encrypt and select Open.

In the next window you will be given a few options as to the type of security that you wish to apply to the file including the level of encryption.

Password and strength

Here are a few explanations as to what each of the check boxes relates to:

User Password is used to open the PDF document (Client wishing to just view it)

Owner Password is used to change security settings (password required to make changes)

Encryption Level

  • 40-bit RC4: Acrobat 3.0 and Later (This is the default option)
  • 128-bit RC4: Acrobat 5.0 and Later (This will be the one most people will use)

Security Options:

  • Printing: Allow to print
  • Modify Contents: Allow to modify
  • Copy: Allow to copy or extract
  • Modify Annotations: Allow to add or modify annotations or form fields
  • Fill In: Allow to input form field and signature (128-bit RC4 only)
  • Screen Readers: Allow to enable accessibility (128-bit RC4 only)
  • Assembly: Allow to modify document assembly (128-bit RC4 only)
  • Degraded Printing: Allow to print degraded mode (128-bit RC4 only)

Now simply enter the required passwords and level of encryption and select Encrypt As.


For myself, I used 128bit RC4 encryption and used separate passwords for the User and Owner fields as I may want to edit the PDF from time to time, but don’t wish other people to edit it, especially if it is a guide that I am posting online for people to download and use.

In the next window will ask you to name the soon to be encrypted file. I’d give it a slightly different name, so that you still have an unencrypted version of the file, and hit Save. This is good as if you forget the password, you won’t be able to access it again.


That’s it. Once you hit Save, it will encrypt the PDF and also prompt you for your password so you can test open it.


Enter either the User or Owner one depending on the access rights you want, hit OK and it will open.

How to decrypt the file

Start PDFill and you will see the familiar main screen

main screen

Select No.3 Encrypt and Decrypt Options and navigate to the PDF that you wish to decrypt and hit Open.

locate pdf

You will be prompted to enter the applicable password for either the Owner or User and OK.

input password

Once you have entered the password you will be given the decrypted options (are you decrypting as Owner or User) and hit Decrypt As.

decrypting as Owner or User

Give the decrypted file a name and then hit Save.

decrypt save as

That’s it. I hope this has helped. Any questions, then please feel free to ask below.

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