Yes. Almost every PDF carries metadata you never typed: an author name, the app that created it, the software that wrote the PDF, and when it was created and last changed. Often there is a title and keywords too, sometimes left over from a template. None of it shows on the page, but anyone who receives the file can read it in a few seconds.

You can see most of it in your PDF reader’s Document Properties. Removing it properly means saving a new copy without those fields, and checking for the other hidden things a PDF can carry, such as comments and form answers, which are not metadata but leak in the same way.

What metadata is in a PDF

A PDF stores metadata in two places. The document information fields are the ones your reader shows. Many files also have an XMP metadata block, which can repeat the same details and add more.

  • Author: often your real name or your computer’s user name, filled in by the app that made the file.
  • Creator and Producer: the app and the PDF software, sometimes with version numbers, such as a word processor, a payroll system or a scanner’s software.
  • Created and Modified dates: when the file was first made and last saved, usually to the second.
  • Title, Subject and Keywords: sometimes set on purpose, often inherited from a template or an older document.
  • XMP extras: depending on the app, things like a document ID, editing tool history or a copyright notice.

Other hidden things that travel with a PDF

Metadata is the part people know about. These are the ones that catch people out:

  • Comments and sticky notes: review remarks such as “check his salary first” stay in the file unless deleted, even when the comments panel is closed.
  • Form field answers: a filled form carries its answers as data, which some systems read directly.
  • A hidden text layer: a scanned PDF that has been through OCR has invisible, searchable text under the image, including any part you thought you had cropped or covered.
  • Content under a box: a black or white rectangle drawn over text hides it on screen, but the text is still in the file and can be copied.
  • Attachments: a PDF can contain other files, shown only in the attachments panel.
  • Earlier versions: some apps save changes by adding to the end of the file, so older content can still be inside it.

Why it matters, with real examples

  • A tenancy agreement made from an agent’s template keeps the previous tenant’s name in its Title field.
  • A CV sent to a new employer has your current employer’s name in Author, because you wrote it on a work laptop.
  • A quotation dated last Friday has a Modified date of this morning, which can raise questions in a dispute.
  • A redacted payslip still shows the full name in the Title field, so the redaction has protected nothing.

How to check what your PDF reveals

  1. Open the file in a PDF reader on a computer. Phone apps rarely show full properties.
  2. Open Document Properties. In Acrobat Reader it is under File, Properties. In Chrome’s and Firefox’s built-in viewers it is in the viewer’s menu. On a Mac, Preview shows it under Tools, Show Inspector.
  3. Read the Author, Title, Subject, Keywords, Creator, Producer, Created and Modified fields.
  4. Open the comments and attachments panels, if your reader has them, and look for anything you didn’t expect.
  5. Try selecting and copying text around anything you covered or blacked out. If you can paste it somewhere, it is still in the file.

Readers show the document information fields, not the XMP block. If you need to see everything, the free command-line tool ExifTool lists both.

What Kopitiam does to metadata

Kopitiam has no metadata editor, but each tool treats metadata in a fixed way, and it helps to know which is which.

  • Edit PDF, Merge, Split, Extract pages, Organise and Redact build a new file from your pages. The original Title, Author, Subject, Keywords and XMP block are not carried over. Creator and Producer are set to pdf-lib, the open-source library Kopitiam uses, and both dates are set to the moment you download.
  • Rotate, Watermark and Add page numbers save changes into the same file. The original Title, Author, Keywords and Created date stay. Producer becomes pdf-lib and Modified becomes the time you download.
  • Compress in Lossless or Shrink photos mode blanks Title, Author, Subject, Keywords, Creator and Producer. The Created and Modified dates and any XMP block stay.
  • Compress in Strong mode rebuilds every page as a picture in a new file, so none of the original fields come across, and the text is no longer selectable.
Clearing metadata does not clear the pages. Tools that build a new file still copy each page as it is, including comments and form fields on that page. Check those separately, and use Redact, not a drawn box, for anything on the page that must go.

A quick way to clean a file before you send it

  1. Check the file as described above and note what you want gone.
  2. Open it in Organise PDF, leave the pages as they are, and click Download organized PDF. The new copy has no original Title, Author, Subject, Keywords or XMP block.
  3. If there is text on the page to remove, such as an IC number on a payslip, use Redact PDF instead and click Redact & download. It also builds a new file, so the same metadata is dropped, and the redacted text is removed rather than covered.
  4. Open the downloaded copy and check Document Properties and the comments panel again before you send it.

The new copy will say it was produced by pdf-lib, with today’s date. That reveals which library wrote the file, not who you are, but it is worth knowing.

Edge cases and when not to use Kopitiam

  • Password-protected or restricted files: Kopitiam can’t open locked PDFs yet. Open the file with its password in your reader and use Print, Save as PDF to make an unlocked copy. That copy is new too, with its own metadata, so check it.
  • Scanned documents: the Producer field often names the scanner or scanning app. If the scan has an OCR text layer, Redact removes that hidden text in the areas you mark, not just the visible image.
  • Very large files: everything runs on your device, so the practical limit is your device’s memory. A 300-page scan may be slow on an older phone; a computer copes better.
  • When the dates matter: if a record must keep its original Created date, don’t run it through a tool that builds a new file. Rotate, Watermark, Add page numbers and Compress in Lossless or Shrink photos mode keep the Created date. Edit, Merge, Split, Extract, Organise, Redact and Strong compression reset it.
  • When you need to set metadata, such as a proper title for a published report: use the app that made the document. Kopitiam can’t write custom fields.

Kopitiam’s PDF tools run in your browser, so the file you are cleaning isn’t uploaded to a server along the way. For sensitive documents, that is half the point.