Protect PDF
Password-protect and encrypt a PDF document
Updated · Guide: How to Password-Protect and Encrypt PDF Files
Processed on our server. Sent over HTTPS to an isolated job, then deleted once you download.
Drop a PDF here
Then set a password to protect it
Max 50 MB
If left empty, defaults to the user password.
Add a PDF to start
Up to 50 MB per file
No daily limit and no watermark on the result.
No account needed
Free to use. No signup, no email, no trial.
How to use Protect PDF
Upload your PDF
Click the upload area or drag and drop the PDF you want to protect.
Set a password
Enter a strong password that will be required to open the file. Optionally set an owner password.
Click Protect PDF
The PDF is encrypted on our server with AES-256 encryption using MuPDF.
Download the protected PDF
Click Download to save the encrypted PDF. Keep your password safe; it cannot be recovered if lost.
What is PDF password protection?
Encrypt a PDF with AES-256 protection and set a password required to open it, plus an optional owner password. Encryption runs on our server with MuPDF, and the file is deleted after download. See our processing model for details.
Password-protecting a PDF means encrypting it so that a password is needed to open it or to change it. Protect PDF locks a document with AES-256 (MuPDF's encrypt=aes-256 write option) so it cannot be opened without the right password.
The tool supports both user passwords (required to open the file) and owner passwords (required to change permissions). Encryption uses the AES-256 standard, the same algorithm used by banks and government agencies to protect sensitive data.
The two password types do different jobs and are easy to confuse. A user password gates opening the file at all; an owner password leaves it readable but restricts printing, text extraction, and modification. Setting only an owner password produces a document anyone can read and nobody can legitimately alter, which is the usual choice for published forms and certificates. Permission flags are advisory: compliant readers honour them, but the content is not cryptographically withheld the way it is behind a user password. For a fuller treatment, see our guide to protecting PDFs with passwords and encryption.
AES-256 encryption means the document content is scrambled using a 256-bit key derived from your password. Without the correct password, the encrypted file is computationally infeasible to decrypt. The strength of the protection depends directly on password quality: use at least 12 characters mixing uppercase, lowercase, numbers, and symbols. Avoid dictionary words or personal information. For documents that need to be visually marked rather than access-restricted, consider adding a watermark instead of or in addition to password protection.
Frequently asked questions
What encryption does the tool use?
The tool uses AES-256 bit encryption, which is the current industry standard for PDF security and is approved for protecting sensitive documents.
What is the difference between a user password and an owner password?
A user password is required to open the document. An owner password controls permissions: printing, copying, and editing. Anyone with the owner password can change these restrictions.
Can a protected PDF be unlocked?
If you know the password, yes: use the Unlock PDF tool on this site. Without the password, recovering the content requires specialized software and can be computationally intensive.
Can I restrict printing and copying without requiring a password to open?
Not with this tool. Protect PDF always requires an open (user) password and does not set print, copy, or edit restrictions.
How do I password protect a PDF for free?
Upload your PDF to this tool, enter a password in the user password field, and click Protect PDF. The document is encrypted with AES-256 on our server and the protected file is ready to download immediately; the upload is deleted after download. No account, no signup, and no watermarks are added to your document.
What happens if I lose my PDF password?
There is no password recovery mechanism. AES-256 encryption is designed so that only someone with the correct password can open the file. Store your passwords in a password manager or other secure location. If you forget the password, the document contents cannot be recovered through this tool.
Can I encrypt a PDF before sending it by email?
Yes, and this is strongly recommended for sensitive documents. Upload your PDF, set a user password, and download the encrypted file. Send the encrypted PDF by email and communicate the password separately through a different channel (phone call, text message, or secure messaging app). This way, even if the email is intercepted, the document remains protected.
Related tools
- Unlock PDFRemove password protection from a PDF
- Watermark PDFAdd text watermarks to PDF pages
- Compress PDFReduce PDF file size while maintaining quality
- Hash GeneratorGenerate MD5, SHA-256, SHA-512, BLAKE3, and 25+ cryptographic hashes to verify file integrity
- Repair PDFFix corrupted or damaged PDF files
Related guides
How to Password-Protect and Encrypt PDF Files
Step-by-step instructions for securing PDF documents with passwords and encryption, including permission controls and security best practices.
How to Convert Word Documents to PDF
A practical guide to converting Word (DOCX) files to PDF while preserving formatting, fonts, images, and page layout across all devices.
Related research
Symmetric Cipher NIST Status 2026: Dataset by Algorithm
A consolidated reference for the symmetric ciphers exposed by Utilavo's encryption tools. Status, key and block sizes, and deprecation dates are sourced directly from NIST SP 800-131A Rev 2 and SP 800-57 Part 1 Rev 5 so the recommendation column is auditable.
PDF/A Archival Conformance Matrix: Levels 1a Through 3u
A structured comparison of the eight PDF/A conformance levels defined by ISO 19005 Parts 1 to 3, each mapped to its practical archival use case. PDF/A-4 (ISO 19005-4:2020) is not yet covered. The matrix exists because the PDF/A levels are commonly conflated, and choosing the wrong level routinely causes archive ingestion failures.