Open Password: Required to open the file — actual security. AES-256 with a strong password is effectively unbreakable.
Permissions Password: Controls printing/copying — trivially bypassed by most PDF software. Do not rely on this for security.
The Redaction Mistake That Exposes Data
Drawing a black box over text does NOT remove it. The text remains in the PDF's data structure — hidden visually but fully extractable:
Real examples: Classified US military documents with "redacted" text that was trivially recoverable.
Proper redaction requires Adobe Acrobat Pro's Redact tool — it permanently deletes the underlying data.
PDF Metadata
Every PDF contains: author name, creation date, edit history, software version. View in Adobe Reader: File → Properties.
Our PDF Compressor strips this metadata automatically when you compress.