About This Tool

PDF Encrypt is a free, browser-based utility for adding an open password to a PDF document. Once encrypted, anyone trying to open the file is prompted for the password by their PDF reader before the contents are decrypted and displayed. This is the same standard PDF security mechanism used by Adobe Acrobat, Foxit, and Preview — fully interoperable with every modern PDF viewer on Windows, macOS, Linux, iOS, and Android.

Under the hood, the tool uses pdf-lib's standard security handler, which applies AES-128 encryption to the document's content streams. The password you enter is the "user password" — the one required to open the file. pdf-lib does not expose a separate "owner password" via this tool, so anyone with the user password can open and view the file normally. The encryption is applied locally in your browser: the original file is read with the FileReader API, encrypted with the chosen password, and the encrypted output is saved via a Blob download.

Because everything runs client-side, your document and your password are never transmitted over the network. There is no signup, no email, no daily limit, and no server. Maximum file size is 50 MB, which comfortably covers reports, ebooks, contracts, and presentations. The tool preserves the original page count, page sizes, fonts, and metadata — only the encryption layer is added on top.

How to Use

1. Upload your PDF — click "Choose PDF" and pick any PDF up to 50 MB. The filename appears next to the button once loaded.
2. Enter and confirm a password — type the password you want to require in both the "Open Password" and "Confirm Password" fields. Tick "Show password" if you want to verify what you typed.
3. Click "Encrypt & Download" — the tool encrypts the PDF in your browser and saves the password-protected file to your device. Send the password to the recipient through a separate, secure channel.

Common Use Cases

• Send sensitive documents by email — encrypt the PDF and share the password via SMS, a phone call, or a password manager, so even if the email is intercepted the file can't be opened.
• Protect contracts and legal paperwork — ensure only the intended recipient can view a signed agreement, NDA, or financial document.
• Share internal reports outside the company — add a password before sending quarterly results, HR documents, or pricing sheets to outside partners.
• Lock down archived records — protect old tax returns, medical records, or personal documents stored on cloud drives or USB sticks.

Frequently Asked Questions

What kind of encryption is used? pdf-lib uses the PDF standard security handler with AES-128 encryption on the document's content streams. This is the same algorithm used by Adobe Acrobat and supported by every modern PDF reader.

Is my PDF or my password uploaded to a server? No. Everything happens inside your browser tab. The file is read with the FileReader API, encrypted with pdf-lib loaded as an ES module, and the result is saved via a Blob download. Your document and your password are never sent over the network.

What if I forget the password? There is no recovery — the PDF standard is designed so that without the password, the file cannot be opened. Choose a password you can remember, or store it in a password manager. We have no way to recover it for you.

Will all PDF readers be able to open the encrypted file? Yes. AES-128 encrypted PDFs are supported by all current PDF readers — Adobe Acrobat / Reader, Foxit, Preview, Chrome's built-in PDF viewer, Safari, Edge, and most mobile PDF apps. Very old readers (pre-2010) may have issues.

Pro Tips

• Use a strong password — at least 12 characters, mixing uppercase, lowercase, numbers, and symbols. A password manager can generate and store one for you.
• Share the password separately from the file — send the PDF by email and the password by SMS, a phone call, or a separate messaging app. If both go through the same channel, the encryption adds little real-world security.
• Combine with other PDF tools — encrypt the final PDF after watermarking, compressing, splitting, or merging so the protected file is the one you actually distribute.

Related Tools — Need to merge multiple PDFs before encrypting the final bundle? Try PDF Merge. Want to split a large PDF and encrypt only the sensitive sections? Try PDF Split. Looking to extract text from a password-protected PDF you still have access to? Try PDF Extract Text. Need to extract images from a PDF before locking it down? Try PDF Extract Images.