Online Tool Store
How it works
- Upload. Drop in a PDF. The security check runs straight away: encryption method, whether it needs a password, all six permissions, metadata, and active content such as JavaScript or attachments.
- Security settings. Choose Encrypt, Change password, Permissions, Remove password or Remove metadata. Generate a password or type your own and watch its strength, then pick what recipients may do.
- Secure. The file is rewritten with qpdf, then re-opened three ways — with no password, with the open password and with the owner password — to prove the settings actually took.
- Download. Compare before and after, copy the passwords, and save the file. Nothing is offered for download until it has passed that check.
What AES-256 PDF encryption does
A PDF is not encrypted as one block. Every string and stream inside it is encrypted separately with the same random file key, and only the key is tied to your password. For the AES-256 method (revision 6, the one in ISO 32000-2):
file key = 32 random bytes
content = AES-256-CBC(file key, random IV per object)
/UE entry = AES-256(hash(open password + salt), file key)
/OE entry = AES-256(hash(owner password + salt + /U), file key)
/Perms = AES-256(file key, permission flags)
The hash is not a single SHA-256: it runs at least 64 rounds mixing SHA-256, SHA-384 and SHA-512, each round depending on the one before, so every password guess costs an attacker real work. Either password can unwrap the same file key, which is why both open the document; the reader then checks which one you used to decide whether the restrictions apply. Changing the password re-encrypts the file with a fresh key, so the old password stops working completely.
How permissions are stored
Permissions are bits in a single 32-bit number, the /P
value. A set bit means allowed:
| Bit | Allows | Setting in this tool |
|---|---|---|
| 3 + 12 | Printing (bit 12 = full quality) | Printing: allowed / low resolution / not allowed |
| 4 | Other changes to the content | Edit content |
| 5 | Copying text and graphics | Copy text & images |
| 6 | Comments and annotations | Add comments & annotations |
| 9 | Filling in existing form fields | Fill in form fields |
| 11 | Inserting, rotating and deleting pages | Insert, rotate or delete pages |
| 10 | Extraction for screen readers | Always allowed, for accessibility |
With AES-256 the same flags are also sealed inside the encrypted /Perms
entry, so a reader can detect a file where someone edited /P
by hand to grant themselves more rights.
How the security score is worked out
The checker starts from how the file is protected, then subtracts for risks it finds:
no encryption 15 · restrictions only 35 · RC4 45 · AES-128 78 · AES-256 92
− 5 identifying metadata − 15 JavaScript − 15 Launch action
85 and above is Strong, 60 and above Good, 30 and above Weak, and anything lower Unprotected. A typical unprotected contract whose metadata names its author and the software that made it scores 10. Encrypting it with AES-256 and removing that metadata takes it to 92.
How the password strength is estimated
Strength is estimated as entropy: length × log₂(character pool), where the pool is 26 for lower case, 26 for upper case, 10 for digits and 33 for symbols. The estimate is then cut for patterns attackers try first — common passwords, repeated characters, keyboard runs and a word followed by digits. The guessing time assumes an offline attacker making ten billion guesses a second, which is pessimistic for AES-256 files because of their slow hash. A generated 20-character password from all four sets scores roughly 115–130 bits on this meter.
FAQ
Is my PDF or password uploaded anywhere?
No. Encryption runs on qpdf, the open-source PDF engine, compiled to WebAssembly and executed inside this browser tab. The file, the passwords and the result never leave your device — once the page has loaded you can disconnect from the internet and it keeps working.
What is the difference between the open password and the owner password?
The open (user) password is needed to view the document at all, and it is what the encryption key is derived from. The owner password unlocks the permission restrictions — printing, copying, editing and so on. Someone with only the open password can read the file but works within the restrictions; someone with the owner password can change them.
Can permissions really stop someone printing or copying my PDF?
Only in readers that honour them, which includes Acrobat, Chrome, Edge and macOS Preview. The permissions are flags inside the file, not DRM: a tool that ignores them can still print or copy the content of any PDF it can open. If the content itself must stay confidential, set an open password — that is real encryption, not a policy.
I forgot my PDF password. Can this tool remove it?
Not an open password. With AES-256 the file is unreadable without it, and there is no back door — that is the point of the encryption. The tool can remove a password when you enter it, and it can lift permission-only restrictions from a PDF that already opens without a password. Only do that for documents you own or are authorised to change.
Should I choose AES-256 or AES-128?
AES-256, unless the file has to open in software older than about 2010. It is the only method defined in the current PDF 2.0 standard, and it uses a slower, salted password hash that makes guessing much more expensive. AES-128 opens in Acrobat 7 and later but only allows plain keyboard characters in the password. The obsolete RC4 method is never offered.
What does "Remove metadata" actually remove?
The document-information dictionary (title, author, subject, keywords, the creating application and producer, creation date) and the XMP metadata packet stored in the catalog. The modification date is kept. Text on the pages, comments, file attachments and the file name you save it under are not changed — check those separately if they identify you.
How we compare
| Feature | Online Tool Store | Adobe Acrobat online | iLovePDF |
|---|---|---|---|
| File stays on your device | ✓ Processed in this tab | ✗ Uploaded to Adobe's cloud | ✗ Uploaded to iLovePDF's servers |
| Separate print, copy, edit and form permissions | ✓ Six controls | Acrobat Pro desktop only | ✗ Open password only |
| Security check of the result before download | ✓ Re-opened and verified | ✗ | ✗ |
| Works offline once the page has loaded | ✓ | ✗ | ✗ |
Uploading a document to a server so that it can be protected from other people is a strange trade. If the file is confidential enough to need a password, PDF Security is the straightforward choice: encryption, permissions and the check all happen on your device, in this tab.