Password-protect a PDF
AES-256 password protection
Formats & limits
Formats & limits
- Accepted formats
- Result
| On a computer | On a phone or tablet | |
|---|---|---|
| Max file size | 500 MB | 150 MB |
Limits on your device depend on its memory. Larger files may still work; the tool warns you first.
How it works
- 01 Choose or drop the PDF you want to protect.
- 02 Type a password. It will be needed every time the file is opened.
- 03 Optionally open More options to limit printing, changes or copying.
- 04 Press Protect PDF and download the encrypted copy.
About this tool
The tool applies AES-256 encryption using your chosen password. Protection depends on password strength, compatible software and the security of your device. Printing and copying permissions may be ignored by PDF software. Keep the original separately and inspect the exported copy with a suitable PDF reader before sharing. Check that it opens as expected and that all required pages and details are present.
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AES-256 encryption
Every page is encrypted with a 256-bit key (security revision 6 of the PDF 2.0 standard). Acrobat, Reader, browser PDF viewers and other current apps open it with the password.
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Permissions you choose
Printing: full, low quality or none. Changes: all, only comments and form filling, only form filling, only page order, or none. Copying text and images: on or off.
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Nothing is uploaded
An on-device engine reads and encrypts the file in a frame your browser keeps offline. No server ever receives the document or the password.
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Content stays as it was
Pages, fonts, images, links and bookmarks are copied unchanged; only the encryption layer is added.
Questions and answers
How strong is AES-256 PDF encryption?
The tool applies AES-256 encryption using your chosen password. Protection depends on password strength, compatible software and the security of your device. Printing and copying permissions may be ignored by PDF software.
What happens if I forget the password I set?
The file can no longer be opened. Hushdesk never sees or stores your password, so it cannot be recovered. Keep the unprotected original, or save the password in a password manager.
Do the printing and copying restrictions really stop people?
Acrobat, browsers and most PDF apps respect them, but they are an instruction to the viewer, not a lock: someone who can open the file could use software that ignores them. The open password is what actually encrypts the content.
What is the permissions password for?
The tool applies AES-256 encryption using your chosen password. Protection depends on password strength, compatible software and the security of your device. Printing and copying permissions may be ignored by PDF software.
Will the protected PDF open on phones and older software?
Current PDF apps on Windows, macOS, iOS and Android open AES-256 files. Very old readers, such as Adobe Reader 9 and earlier, cannot.
Does adding a password change the pages or the file size?
No. The pages are copied as they are and only encrypted, so the size stays about the same. To make the file smaller, compress the PDF before you protect it.