A Tutorial for Free PDF Encryption, How to Password Protect A PDF File


PDF is the most frequently used file format for document exchanging and sharing on the internet.PDF is popular because normally people can't easily edit it. However, with more and more PDF editing tools developed, PDF users seem to have difficulty keeping their PDF files from being altered and edited. Under this circumstance, adding a password to encrypt A PDF would be a considerable choice to secure your file.

Today we'll introduce you to some practical methods of how to password protect a PDF file. You can encrypt a PDF by using EasePDF Online PDF Protector, Microsoft Office, Mac Preview, Adobe Acrobat DC, etc. Most of these tools are free.

Part 1. Reasons for Password Protecting PDF

1. To Restrict Certain Usages

There are two different types of PDF password encryption. One is to protect the whole PDF file itself from being opened and read. Another is to have a password that only restricts certain usage, like to forbid editing, copying or printing. The latter type of passwords is much easier to be cracked and unlocked. So choosing the right type of password and setting the password complicated could make it difficult to unlock a PDF.

2. To Protect Copyright

Another important reason why we need to lock a PDF file is to protect the content and information in your PDF from copyright infringement. Some people who have access to your PDF file might likely reproduce your work without permission, which violates the author's intellectual property rights. Some people might consider encrypting a PDF is way too complicated and inconvenient for protecting copyright. For those users, there's another simple way to declare your copyright - eSign your PDF.

3. To Keep Commercial Profit

Although a PDF is considered not technically a true ebook, many ebook readers will still ask for PDF format ebooks because they can keep the same output on different devices. Therefore PDF ebooks still have a great market on e-publishing business. And for those PDF ebooks owners, using encryption to protect their PDFs from being shared for free immoderately is vital for keeping their selling profits. Another potential abuse for paid ebooks that need to be prevented is printing, adding a password to restrict the file being printed is the lowest cost protection.

Tips: EPUB is another common and popular ebook format that compatible with most readers. You can convert PDF to EPUB in case some devices don't support the PDF format.

4. To Seal Confidential Document

In business, we often have to deal with confidential documents like business contracts, price lists, and internal documents that need high privacy and confidentiality. It is very important to keep these kinds of files only accessible to certain people and unalterable for any person. And the most effective way to do that is to seal the confidential document by adding an encryption password.

5. To Keep Content Integrity

Encrypting a PDF file is also a way of keeping the content integrity of a document. If a PDF file you send to other people is to be printed and filled out, you might need to make sure the content that you embedded stayed unalterable. Another occasion where content integrity is important is if you have made some modification opinions like highlight, strikeout, notes, etc to paperwork or an article. To lock this PDF file, you've kept those notes from being deleted or altered.

Part 2. Ho to Password Protect A PDF File

The rest of this post will show you 5 simple yet practical methods to lock your PDF, you can choose the best solution according to your device and encryption requirements.

Method 1. Using Online Encryption: EasePDF

Online PDF encryption is a way for PDF protection that you can disregard different devices. As long as you have an internet connection you're good to go. EasePDF has more than 30 PDF-related tools, including Word to PDF Converter, Excel to PDF Converter, eSign PDF, Split PDF, Merge PDF, Protect PDF, Unlock PDF and so on. Now let's try to protect PDF on EasePDF.

Step 1. Go to EasePDF homepage and click on "Protect PDF" on the "All PDF Tools" menu.

Click Protect PDF

Step 2. Choose the PDF file you want to add a password and upload it to the server. The file could be from your computer, smartphone or cloud drives like Google Drive.

Protect PDF Upload PDF Files

Step 3. Set a password to encrypt your PDF. Enter your password twice on two rows of the password box. The password you set will be 256-Bit AES encryption protected, so it's with high security. If the passwords you entered didn't match, the system will tell you to re-enter. When your passwords match, the system will highlight the "Protect PDF" button. Click on it and your PDF file will be automatically encrypted with the password you set.

Enter Passwords to Protect PDF

When your PDF file is successfully encrypted, the system will provide you a download link and some "save to cloud drives" links, just choose whatever you want.

Method 2. Password Protect PDF on Mac

Our Mac computer comes with Preview, a program that's capable of opening most documents and image formats. Mac Preview can help us to export a Word document as a PDF. It also supports password protecting PDF in just a few steps.

Step 1. Launch Preview on Mac, click the "File" menu in the upper-left corner and choose"Open". Select the PDF file you want to password protect from your computer and click the "Open" button.

Step 2. Go to the "File" menu again and choose "Export" from the drop-down menu. On the popup menu, enter a file name to your exported file and choose a location to save. Then tick the "Encrypt" box on the bottom of the window. Two blank boxes will show up, now enter the password you would like to encrypt twice, then click the "Save" button.

Protect PDF Mac Preview Encrypt

Step 3. Test the encrypted PDF file. Now you need to open your newly encrypted PDF in Preview. If a password prompt screen appeared, that means you've successfully password protected your PDF document. Now enter your password to unlock it and see if you remember the password correctly.

Method 3. Password Protect PDF with Microsoft Office

In the earlier version of Microsoft Office (from Office 95 to Office 2003), password protection is considered very weak. But since Office 2007, Microsoft switched to the Advanced Encryption Standard (AES) with a 128-bit key. That means Microsoft Office can offer users real and strong encryption to protect their documents.

There are two modes of password protection on Office. One is to fully encrypt the document, another is to restrict the editing access only. And please keep it in mind that the Office encryption only works for modern document formats like .docx. That means if we're using Office to password protect a PDF file, Office will convert it to a .docx Word document at first. Now let's get started.

Step 1. Open your PDF file with Microsoft Office. Run Office on your computer, go to the "File" menu and click on "Open" on the left side. Locate the PDF file that needs to be encrypted and then choose "Open".

Protect PDF Office Open

Step 2. A warning message will pop up to tell you that the PDF document you intend to open will be converted into an editable form. Just click the "OK" button.

Step 3. Go to the "File" menu and choose "Save As" option. Select "PDF (*.pdf)" as the output format on the drop-down file type list.

Protect PDF Office Save As PDF

Step 4. Click "Options" on the saving setting window. On the "Options" window, tick the "Encrypt the document with a password" box and click the "OK" button.

Protect PDF Office Encrypt

Step 5. Enter the password you would like to set twice, and press "OK".

Office Encrypt PDF Document

At last, name your PDF and select a saving location on the saving setting window, then click the "Save" button. Congratulations, you've set password protection for your PDF.

Method 4. Password Protect A PDF in Adobe Acrobat

In Adobe Acrobat, there are two types of passwords available: "Document open password" and "Permissions password". With that, you can either limit access to open a PDF or restrict certain features like editing and printing. But you can not restrict from coping with a PDF in Adobe Acrobat.

Step 1. Open the PDF with Adobe Acrobat and choose "Tools"→"Protect"→"Encrypt"→"Encrypt with Password". Click "Yes" to change the security if the warning prompt showed up.

Step 2. Tick the "Require A Password To Open The Document" box on the encryption window. Then enter the password on the typing field. The system will evaluate your password strength on the right side. The recommended password strength is "Strong" and above.

Adobe Acrobat Encrypt Document

Step 3. On the Options window, choose a suitable Acrobat version from the "Compatibility" drop-down list. You should not choose a version that is too new because it might not compatible with many Acrobat versions. For instance, Acrobat 7 cannot open a PDF encrypted for Acrobat 8 and later. Then choose the encryption option from the list below.

Adobe Acrobat Encrypt Document Options

Step 4. Click "OK". A prompt box will pop up, please retype the password you enter at step 2 and click "OK". Now you've got your PDF document password protected in Adobe Acrobat.


If you want to encrypt a PDF on Mac computer, please use the Preview app comes with Mac. For Windows users, you can choose to lock your PDF with Microsoft Office. Adobe Acrobat and EasePDF can work on both computer systems. And EasePDF supports password protection on smartphones as well.

Now let's think about it, how can we do the opposite? Here's an useful post about How to Unlock A Password Protected PDF File, which might be of great help. Got more PDF tips? Feel free to let us know by leaving a comment or contact us.

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