The Complete Guide to PDF Protection and Unlocking: Passwords, Permissions, and Security Strategies

PDF protection is the first line of defense for document security, whether you need to prevent unauthorized opening, block text copying, or restrict printing. Use Protect PDF to set passwords and permissions in one click, and use Unlock PDF to remove restrictions when the password is known.

What do you want to do? (10-second decision)

Set a password so others cannot open the PDF → Set an "open password"
Let others view but not copy/print/edit → Set "permission restrictions"
Remove editing/printing restrictions from a PDF → Use Unlock PDF
Forgot the password and cannot open your own PDF → See the "Common Questions" section
Not sure about the difference between the two passwords → Keep reading

Two Passwords, Two Completely Different Purposes

Open Password vs Permission Password Comparison

The PDF standard defines two different password types. Many people confuse them, but understanding the difference is critical:

Comparison	Open Password (User Password)	Permission Password (Owner Password)
Purpose	Cannot open the file without the password	File can be opened and viewed, but specific actions are restricted
Typical scenario	A hard lock for sensitive files sent to non-designated recipients	A soft restriction for "viewable but not copyable" documents
Security strength	Strong: file content is encrypted	Weak: depends on viewers honoring permission flags
Can it be bypassed	Cannot decrypt without the password	Some tools can ignore permission flags
In our tools	A password prompt appears after upload; processing continues only after correct input	Restrictions are removed automatically, no extra action required

A permission password is not real encryption

A permission password only sets a "gentleman's agreement" flag inside the PDF. Mainstream PDF readers (Adobe Acrobat, Preview) will honor these restrictions, but technically, a permission password does not encrypt file content. So do not rely on permission passwords alone to protect confidential information. Use them together with an open password.

Protect a PDF: Choose the Right Strategy by Scenario

Scenario 1: Full Lockdown — Only people with the password can open it

Best for highly confidential files such as contracts, payroll slips, and medical reports.

In Protect PDF, set an open password. The file content will be encrypted with AES-256, and anyone without the password will only see an inaccessible file.

Password strength recommendations

Use at least 12 characters with uppercase/lowercase letters, numbers, and symbols
Avoid easily guessed information such as birthdays or phone numbers
Send the password via a secure channel (for example, in person or encrypted messaging), and do not put it in the same email as the PDF

Scenario 2: Viewable but restricted — Disable copy, print, and edit

Best for bid documents, proposal submissions, and internal review drafts.

In Protect PDF, enable permission restrictions:

Disable text copying — Prevent selecting and copying text with Ctrl+C
Disable printing — Prevent output to paper or another PDF
Disable editing — Prevent changes to document content and annotations

Scenario 3: Layered protection — Password + permissions + watermark

Layered Document Security: Encryption, Watermark, Flatten

For the highest-security cases (such as bids and legal files), use this layered approach:

Protect PDF — Set both an open password and permission restrictions
Add Watermark — Stamp "For Bid Use Only" or your company mark
Flatten PDF — Make watermarks and form elements permanent so they cannot be removed

Unlock PDF: Remove Restrictions Legally

Unlock PDF helps you remove passwords and permission restrictions from PDFs.

Permission restrictions (editing/copying/printing disabled)

If your PDF can be opened but cannot be edited or copied, it likely has only a permission password. After uploading to Unlock PDF, the tool will automatically remove these restrictions with no password required.

Open password (cannot open at all)

If your PDF requires a password to open, the tool will show a password input prompt after upload. You can continue unlocking only after entering the correct password.

What if you forgot the password?

If you completely do not know the open password, we cannot help "crack" or "bypass" it. That is exactly what the PDF standard is designed to prevent. We recommend:

Contact the file sender to get the password
Check your email history to see whether the password was shared
Look up your password manager

Common Questions After Protection

Can a protected PDF still be merged/compressed/converted?

Yes. In all Dpdf tools, when you upload a protected PDF, a password prompt appears automatically. After entering the correct password, you can continue with operations such as Merge, Compress, or PDF to Word. Files with only permission passwords are handled seamlessly after restrictions are removed automatically.

Will encryption make the file much larger?

Almost never. PDF encryption is stream-based, and the file-size impact is usually under 1%.

Are encryption and digital signatures the same thing?

No. Encryption controls who can open and operate the file; digital signatures prove whether the file has been tampered with. They can be used together, but neither replaces the other.

Correct order for signing and protection operations

Operations such as encryption, watermarking, and flattening will invalidate an existing digital signature. The correct order is: finish all processing first, then sign last.

Permission password vs open password: which one should you set?

Your need	Recommended setup
Prevent all unauthorized viewing	Open password (required)
Allow viewing but block copy/print	Permission password + watermark
Highly confidential + anti-copying	Open password + permission password + watermark + flattening
Archive-only storage	Open password only