How to use
Drop the PDF you want to encrypt or click “Choose files”. If it is already password-protected, remove that first with “PDF Unlock (Known Password)”.
Enter the “Password to open” and type it again in the confirmation field. Use “Show” to check it. Short, repeated-character or digits-only passwords get a warning.
If you want, tick “Restrict printing, editing and copying” and enter an owner password that differs from the password to open.
Click “Set password and save”. The saved file is read back, and the page count and password behaviour are checked and shown.
Save it as “name_protected.pdf” with “Save the protected PDF”. Keep the password somewhere safe.
What it does
AES 256-bit encryption
Every string and stream is encrypted with AES 256-bit from PDF 2.0 (ISO 32000-2, revision 6). The key, salts and initialisation vectors are generated freshly from your browser’s random source each time.
Always read back after saving
The saved file is opened again to confirm the page count, that the right password opens it, and that it does not open without a password or with a wrong one. If the check fails, no file is produced.
Honest about restrictions
Print / edit / copy limits are a request that compliant software honours. Some apps ignore them and some tools remove them, so they are not strong protection. The page says so.
A confirmation field prevents typos
You cannot continue unless the confirmation matches (the owner password has one too). Easy-to-guess passwords get a warning, and the password is never stored, logged or sent.
Everything in your browser
Reading, encrypting, checking and saving all happen on your device.
Use cases
- Put a password on a contract or invoice before sending it by email
- Encrypt a PDF with personal data before placing it in a shared folder or the cloud
- Make a handout harder to print or copy (note that this is not strong protection)
- Encrypt PDFs you carry around in case a device is lost
Supported formats
Input
Output
Capability matrix
| Feature | Support | Notes |
|---|---|---|
| Password to open the file | Supported | — |
| AES 256-bit encryption (PDF 2.0, revision 6) | Supported | The app that opens it must support PDF 2.0 encryption |
| Print / edit / copy limits (owner password) | Partial | A request that compliant software honours; not strong protection |
| Read-back check after saving | Supported | Page count and password behaviour are verified |
| Change the password of an already encrypted PDF | Not supported | Remove it first with PDF Unlock (Known Password) |
| RC4, AES 128-bit or other older methods | Not supported | Only AES 256-bit is written |
| Certificate (public-key) encryption | Not supported | — |
| Keep digital signatures valid | Not supported | The file is rewritten, so signatures become invalid |
| Recover a forgotten password | Not supported | Impossible. Keep the password safe |
| Batch processing | Not supported | One file at a time |
Limits & notes
- Up to 200 MB per file. Large files can take tens of seconds.
- Only AES 256-bit (PDF 2.0) is written. Some old PDF viewers and libraries cannot open it.
- Only the first 127 bytes of the password are used. It is normalised with the standard SASLprep rules, so full-width letters and the like become half-width; control and private-use characters are refused. Passwords with characters other than plain letters and digits may not open in some apps.
- A forgotten password cannot be recovered by this tool or anything else.
- The file is rewritten, so digital signatures become invalid. Page content is unchanged.
- Print / edit / copy limits are not strong protection. Protect anything important with the password to open.
Privacy & safety
Loading, encrypting, checking and saving all happen in your browser. The PDF, the password you type and file names are never sent to or stored on a server, and are not placed in URLs, logs, browser storage or usage analytics.
FAQ
Can I recover the PDF if I forget the password?
How strong is the encryption?
Are the print and copy limits safe?
Are my PDF and password uploaded?
Which apps can open the protected PDF?
Can I change the password of a PDF that already has one?
Related tools
PDF Unlock (Known Password)
Remove the open password and the editing, printing and copying limits from a PDF whose password you know. Use it on your own files or files you are authorised to open. It cannot guess or crack passwords, and your PDF is never uploaded.
Compress PDF
Drop a PDF to cut its size. Only photos and scans are recompressed, so text and graphics stay crisp. Your PDF is processed on your device and never uploaded.
Merge PDF
Drop several PDFs, put them in order, and get one PDF. You can also choose which pages to take from each file. Nothing is uploaded — merging happens on your device.
Images to PDF
Drop images, put them in order and get one PDF. Choose page size, orientation and margins; phone photos are rotated correctly. Images are converted on your device and never uploaded.
PDF Editor
Lay text (Japanese included), shapes, arrows, a highlighter, freehand drawing and images on top of a PDF, and fill in its form fields. Everything is written as PDF vectors and real text, never as a picture. Rewriting the original text and true redaction are not possible.
PDF Extract
Take the text, images, links, attachments, form values and bookmarks embedded in a PDF, for the pages you choose. Images stay as embedded (JPEG untouched). Your PDF never leaves your device.
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