Metadata scrubbing module (Scrubber)

The Scrub metadata module (sometimes called the Scrubber) removes in one go all the descriptive information embedded in the PDF — author, title, subject, keywords, creator, internal dates, technical identifiers. It is a recommended step before distributing any sensitive document, because this information can inadvertently reveal personal or organizational data. You reach this module from the Security category of the Dashboard.

Difference from the Metadata module

HtkPDF offers two distinct modules for acting on metadata:

The Metadata module is the everyday tool for filling in your documents' identification information. The Scrub metadata module is the reference tool before any public or anonymous distribution.

What is erased

The scrubbing action removes every descriptive field of the PDF, including:

• Title;
• Author (often filled with the system user name — a risk of identity leakage);
• Subject;
• Keywords;
• Creator (the source application — can reveal the software used);
• Producer (the export engine);
• Dates (internal creation and modification, which may differ from the Finder dates).

These are the fields of the PDF's information dictionary, the ones macOS exposes. Two limits worth knowing: an XMP stream (extended metadata written by InDesign, Acrobat or a camera), if any, is left untouched — HtkPDF cannot reach it; and on saving, macOS writes its own Producer ("Quartz PDFContext") and fresh dates, those of the save.

Concretely, the cleaned PDF no longer carries a title, an author, a subject, keywords, or any trace of the originating software. Indexing tools (Spotlight, document managers, search engines) will only have access to what the document's own text exposes.

What is not erased

The Scrubber module does not touch the following elements:

• the visible content of the pages (text, images, drawings);
• the annotations (notes, highlights, forms);
• the signatures applied (text or image);
• the watermarks and Bates numbering applied;
• the structure of the document (pages, outline, hyperlinks).

To clean these elements as well:

• for the annotations: use the Clean annotations button of the Flatten module;
• for identifiers visible in the content (for example a name in a page header): use the Redaction module;
• to prevent the user's name being extracted from a completed form field: flatten the form after filling it in (Flatten module).

How to use it

The module presents a minimal interface:

1. Open the Scrub metadata module from the Dashboard;
2. Click Erase metadata;
3. A confirmation dialog appears: "Erase metadata? This action cannot be undone. All indexing information will be removed from this PDF file.";
4. Confirm by clicking Erase.

The operation is instantaneous. Afterwards you return automatically to the Dashboard and the information area now shows Author: Unknown, Date: Unknown, and so on, confirming that the scrub succeeded.

Applying and history

Like every editing operation:

• scrubbing creates a checkpoint in the History;
• the document moves into pending changes;
• the result is only permanent once it has been explicitly saved through the Save button on the Dashboard (⌘S).

As long as you have not saved, you can go back to the version with metadata through the History module. Once saved, the metadata is permanently erased from this file (but it may survive in a source file, provided you kept one separately).

Typical use cases

• Before public distribution: removing the author's name, the source software and the internal dates before putting a PDF online on a website or in a public repository;
• Before sending to an external recipient: avoiding transmitting metadata that reveals the sender's organization or software version;
• Anonymous documents: producing a PDF free of identification, for example for an anonymous application, a protected disclosure or a confidential publication;
• Responding to a tender: removing traces of earlier versions and collaborators before sending the final version;
• After an editing chain: a PDF that has passed through several editors can accumulate contradictory or obsolete metadata; a final scrub resets the counter.

Best practices

• Combine with password protection: for a highly confidential document, chain scrubbing + flattening + encryption (Protect module) before distribution;
• Check after scrubbing: open the file's Information in the Finder (cmd+I) or in Preview (⌘ I) to confirm that the fields really are empty;
• Keep an original copy: scrubbing is destructive. If you expect to have to re-edit or fill in this metadata later, keep an unscrubbed copy;
• For a legal document, scrubbing alone does not guarantee anonymity: the visible content (headers, footers, signatures) can reveal the author. Combine it with a careful read and, if needed, the Redaction module.