Protect PDF
Add a password to your PDF
Drop .pdf files here
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How it works
- 1. Upload your .pdf file
- 2. Enter your email address
- 3. Download your converted file
Always Free
25 free operations per year per email address. Resets every January.
About Protect PDF
Protecting sensitive documents with a password ensures that only authorised recipients can open them. PDF Ninjas adds password protection to your PDF so that anyone who receives it will need the correct password to view the content. Perfect for financial documents, confidential reports, legal agreements, tax forms, and any file you want to share securely over email or cloud storage.
Password protection is enforced at the PDF level — the password prompt appears in every PDF reader, on every platform. Recipients cannot bypass it without the correct password, regardless of what device or application they use.
Protect PDF — Complete Guide
When you should password-protect a PDF
Password protection is worthwhile any time you send a document containing personal, financial, medical, or legal information. Bank statements, payslips, tax returns, medical results, contracts, and HR documents are all suitable for password protection before emailing. Even if you trust the recipient, email is not a secure channel — messages can be forwarded, accounts can be compromised, and attachments can be stored in insecure inboxes for years. A password-protected PDF ensures the document is unreadable to anyone who intercepts it or gains access to the email thread later.
Choosing a strong password
The security of a password-protected PDF depends entirely on the strength of the password. Avoid short, dictionary-word passwords — a determined attacker can crack weak PDF passwords using brute-force tools in minutes. A strong password is at least 12 characters long, combines upper and lowercase letters, numbers, and symbols, and is not based on a word or name. Use a password manager to generate and store a strong random password. Never include the password in the same email as the PDF attachment — send the password separately via a different channel such as SMS or a messaging app.
Sending the password securely
Once you have protected your PDF, the secure workflow is to send the file by email as usual, then communicate the password to the recipient by a separate means — a text message, a phone call, a WhatsApp message, or an encrypted messaging app. This two-channel approach means that even if the email is intercepted, the attacker has the encrypted file but not the password. Warn your recipient to expect a separate password message, so they know to look for it rather than assuming the document is password-free. After the recipient confirms they can open it, there is no need to store the password yourself.