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CALCPARK

PDF Unlock

Remove usage restrictions (no printing, copying or editing) from PDFs, and take the open password off files whose password you know. Decryption happens in your browser.

Files stay on your device
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How to use it

  1. Drop one or more PDFs. Each file is inspected and labelled: “Restricted: printing, copying”, “Open password required” or “Not encrypted”.
  2. If a file asks for its open password, type it in the password field. One password is applied to all files that need one.
  3. Press “Remove protection”. The list shows which files were unlocked and why any could not be.
  4. Download the unlocked PDF (or the ZIP). The output opens in any viewer without a padlock and allows printing, copying and editing.

Example

A bank statement that opens normally but refuses to print or copy text: the checker reports “Restricted: printing, copying text, editing”. No password is needed – press “Remove protection” and download statement-unlocked.pdf, which prints and lets you copy the figures. A payslip that asks for your date of birth to open: type it (e.g. 19851203), run the tool, and the saved copy opens directly.

How unlocking works

PDF encryption (ISO 32000-1, section 7.6) has two passwords. The user (open) password is required to display the file; the ownerpassword only guards the permission flags. When a file opens without asking, its user password is empty, and the encryption key can be derived from that empty password – which is why restrictions can be removed without knowing the owner password. The content was never hidden, only the viewer was asked to respect a flag.

The tool first opens each file with pdf.js to read the permission flags (table 22 of the standard) and the metadata, then loads it with @cantoo/pdf-lib, a pdf-lib fork that implements the standard security handler: it computes the key from the password (MD5/RC4 for revisions 2–4, SHA-256 for revision 6), decrypts every string and stream, and writes a new file without an /Encrypt dictionary. Title, author, subject and keywords are copied over from what pdf.js read.

What it cannot do

  • Open a file without its user password. There is no brute-force, dictionary or “recovery” mode.
  • Handle public-key (certificate) encryption or custom security handlers used by some DRM systems.
  • Remove digital signatures or make a signed document editable without invalidating the signature.

Sources: PDF 32000-1:2008, 7.6 Encryption, pdf.js – getPermissions / PermissionFlag, @cantoo/pdf-lib – encryption handling.

Questions

Is it legal to remove PDF restrictions?
Removing restrictions from documents you own or are allowed to use (your own statements, invoices, reports) is normal practice. Circumventing protection on copyrighted material you are not licensed to copy may be illegal where you live.
I do not know the password. Can the tool open the file anyway?
No. If the file needs an open password, the content is encrypted with a key derived from that password. Without it there is nothing to decrypt. Ask the sender for the password.
Why does the unlocked file still show "Secured" in Acrobat?
Make sure you opened the downloaded copy, not the original. The output has no encryption dictionary at all; a signed document, however, may still display a signature panel.
Does unlocking change the content?
No. Pages, text, images, links, bookmarks and forms are decrypted and written back as they were. The file is re-serialised, so its byte size may differ slightly.