Encrypt your PDF files online free with a strong custom password. Add high-level password protection to prevent unauthorised editing, printing or copying.
Select a PDF file to add password protection — or drag & drop
Dudi Protect PDF is a fast, 100% free, browser-based tool from Dudi PDF Editor that encrypts any PDF document with a strong password in seconds. Whether you are securing confidential business reports, legal contracts, salary slips, bank statements, medical records, tax documents, personal ID scans or sensitive personal files, this tool does it all without installing software, creating an account, verifying an email or paying any hidden fee. Unlike most online PDF protectors, your file and your passwords are never uploaded to a remote server. The entire process runs inside your browser using the pdf-lib JavaScript library — your PDF is read from your device, encrypted in memory, and the finished file stays on your device until you press the Download button. That means your confidential documents never leave your computer or phone, and your passwords never travel across the internet at any point. There is no signup, no watermark, no daily limit and no page-count restriction beyond your device's memory. Dudi Protect PDF gives you two separate passwords, following the PDF standard. The user password (also called the open password) is required before the file can be opened at all — without it the content cannot be read. The owner password (also called the permissions password) controls what a reader is allowed to do after opening, such as printing, copying text and images, editing content or adding annotations. You can set just the user password, just the owner password, or both, depending on how strict you want the protection to be. Four permission toggles let you allow or deny printing, modifications, copying and annotations individually, and these restrictions are enforced by PDF readers once the owner password is set. The tool includes a live password strength meter that turns red for weak, yellow for medium and green for strong as you type, so you can immediately see whether your password is safe enough. You can also show or hide each password while typing to avoid typos, and the confirmation field prevents you from locking a file with a password you mistyped. Encryption uses AES-256 through pdf-lib, the same industry-standard cipher used by professional PDF software, so the output opens correctly in Adobe Acrobat, Chrome, Edge, Safari, Firefox and every common PDF reader, always prompting for the password you set. Because the tool never downloads automatically, nothing is saved to your disk until you choose it: after the protection is processed, a Download button appears and you decide when to save the file. The downloaded file is always named Dudi PDF Editor Protect PDF.pdf, and if you protect another file in the same session it becomes Dudi PDF Editor Protect PDF (2).pdf and so on, so your files stay clearly identifiable. The layout is fully responsive, so the password fields, permission toggles and action buttons all stay easy to use on a small Android phone as well as on a large desktop monitor. After the first page load the libraries are cached, so the tool often keeps working even on a weak connection. Remember that there is no password recovery — if you forget the user password, the file cannot be opened, so always store your password safely. If you need more tools, Dudi PDF Editor also offers Unlock PDF, Merge PDF, Split PDF, Compress PDF, Rotate PDF, PDF Page Numbers, Sign PDF, Word to PDF, JPG to PDF, editing, watermarking, cropping, OCR, image conversion and many other privacy-first utilities that all run locally in your browser with the same no-upload guarantee.