Protect PDF with Password

About this tool

The UnblockPDF Protect tool adds password-based encryption to your PDF documents, restricting who can open, print, edit, or copy content from the file. The entire encryption process runs inside your browser using industry-standard AES (Advanced Encryption Standard) algorithms, which means your password and document are never transmitted to any server. The tool supports two types of passwords. The user password (also called the open password) is required to open the PDF document at all. Without entering the correct password, the content remains completely inaccessible. The owner password (also called the permissions password) controls what actions are allowed once the document is opened, including printing, editing, copying text, filling forms, and extracting pages. You can set both passwords independently, allowing you to distribute a document that anyone with the user password can read but only someone with the owner password can modify or print. The encryption is applied using AES-128 or AES-256 depending on the compatibility settings you choose. AES-256 provides the strongest protection and is recommended for highly sensitive documents. AES-128 offers slightly broader compatibility with older PDF readers while still providing robust security. The protected PDF is fully compatible with all major PDF readers including Adobe Acrobat, Adobe Reader, Preview on macOS, Foxit Reader, and browser-based PDF viewers. Recipients simply enter the password when prompted to access the document according to the permissions you have defined. Common use cases include protecting confidential business proposals before sharing with external stakeholders, securing financial documents and tax records with password access control, restricting printing and copying of intellectual property documents, adding access control to HR documents containing personal employee information, and protecting draft manuscripts from unauthorized distribution. The encrypted output can be downloaded immediately. The tool supports files up to 50 MB for anonymous users and 100 MB for registered accounts, and works across all modern browsers on desktop, tablet, and mobile devices.

Common use cases

Tips for best results

• Use a strong password with at least twelve characters combining uppercase, lowercase, numbers, and symbols for maximum security.
• Set separate user and owner passwords to allow reading access while restricting editing and printing capabilities independently.
• After protecting the document, use the Flatten tool first if you want to permanently lock annotations and form field content.
• Store your passwords securely, as UnblockPDF does not retain any password information and cannot recover access to locked documents.