Protect PDF
Add an AES-256 password to open a PDF. Protect a new file or replace its existing password, then download the encrypted document in your browser.
PDF to protect
One PDF selected
The original file stays unchanged. A protected copy will be downloaded.
Your protected PDF is ready
Your protected PDF is ready to download.
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Use PDFArmy for your next PDF task.
Privacy note: Your PDF and passwords are processed locally in your browser. They are never sent to PDFArmy.
Add a password to open a PDF
Use PDFArmy Protect PDF to encrypt a document with an AES-256 open password. Choose a PDF, set and confirm a new password, then download a protected copy. If the source PDF already requires a password, enter it in the current password field before setting the new one.
The original file stays on your device and is not changed. Only the downloaded copy is protected.
How to use the Protect PDF tool
- Select a PDF. Browse for a document up to 50 MB, or drop it into the upload area.
- Enter its current password if needed. Leave this field blank when the PDF opens without a password.
- Choose a new password. Enter at least 8 characters, then confirm the same password. A longer, unique password is stronger.
- Name the protected copy. Keep the suggested name or enter another PDF filename.
- Protect and download. The browser creates and checks the encrypted PDF, then starts the download.
- Keep the password safe. PDFArmy does not store it and cannot recover a forgotten password.
What does PDF password protection do?
The tool encrypts the document using AES-256 and requires the new password to open it in a compatible PDF reader. Password protection is different from restrictions on printing, copying, or editing. This tool does not set those restrictions, and some PDF software may allow those actions after the document is opened.
A strong, unique password helps protect the file. Anyone with the password can open the document, so share it only with people who should have access.
File types and limitations
This tool accepts one PDF up to 50 MB. If the PDF already has an opening password, enter the correct current password before adding the new one. Damaged, unsupported, or unusually complex PDFs may fail to process. Very large documents may take longer or use substantial device memory.
Keep the original document and check that the downloaded copy opens with the new password before sharing it. Older PDF readers may not support AES-256 encryption.
Privacy and file security
Your PDF and passwords are processed locally in your browser. They are not uploaded to PDFArmy. The qpdf WebAssembly encryption library loads from jsDelivr, so an internet connection is needed to load it. The library processes the file on your device; your PDF and passwords are not sent to the CDN.
This tool uses the open-source qpdf engine and its browser WebAssembly wrapper.
Frequently asked questions
Does the PDF need a password to open?
Yes. The new password is an AES-256 open password. A compatible PDF reader will ask for it before opening the document.
Can I protect a PDF that already has a password?
Yes. Enter the current password in the optional field, then set and confirm the new password. The downloaded copy will use the new password.
Will the password stop people from printing or copying?
No. This tool adds a password required to open the file. It does not restrict printing, copying, or editing after the PDF is opened.
Are my PDF or passwords uploaded?
No. The PDF and passwords stay in your browser during processing. The qpdf WebAssembly library is downloaded from jsDelivr, but your file and passwords are not sent to the CDN.
What if I forget the new password?
PDFArmy does not keep your password and cannot recover it. Keep a secure copy of the password before sharing or storing the protected PDF.
Can older PDF readers open the protected file?
The file uses AES-256 encryption, which some older PDF readers may not support. Use an up-to-date PDF application and check the downloaded copy before sharing it.