PDF metadata

Six are editable: Title, Author, Subject, Keywords, Creator, and Creation Date (shown in your device's time zone). The Modification Date updates automatically to the save-time moment, and the Producer is rewritten with this tool's signature on save - so those two are display only (each field has a note beside it); saving exports a new PDF, the original file is left untouched.

The PDF itself never carried that field (many PDFs only have the Producer written by their generator). Empty fields show "not set"; on save an empty box stays empty, a filled-in value gets written.

No. Encrypted PDFs cannot be parsed inside the browser - the page suggests opening the PDF in a reader, entering the password, saving an unencrypted copy, and uploading that instead. This tool neither decrypts nor strips passwords.

No. Parsing and writing with pdf-lib both happen inside your browser; the file never leaves the machine, and reloading clears it.