Removing hidden information from a PDF before sharing it

What you see on a PDF's pages is not everything the file holds. It may carry the author's name, notes from a review, a spreadsheet attached months ago, text that was never visible, and whole earlier versions of the document. Sending it on can send all of that too.

PDF by Zaweba shows you what is there before you share. Choose Protect, then Remove hidden information, and you get a list of what the PDF carries, with counts, and you tick what to remove. Sanitise document removes all of it at once.

What the list covers

The list goes through eleven kinds of hidden or easily missed content.

Document details and XMP are the file's descriptive information: title, author, subject, keywords and more. They often hold a person's name or an internal file path nobody meant to share.

Attached files can be anything, from a supporting spreadsheet to an old draft.

Comments are review notes and marks, sometimes frank ones written for colleagues, not clients.

Form fields are live boxes and their values.

Invisible text is text in the file that isn't drawn on the page, such as the hidden text layer some scanners add.

Content off the page is material placed outside the visible area, perhaps left over from a layout program.

Bookmarks, scripts and actions, and links make up the next three.

Earlier versions are the one people forget. Ordinary saves add changes to the end of a file, so the previous state can still be inside it. If you edited out a figure, the earlier version may still have it.

Choosing what to remove

The counts help. Two comments and one attachment tell you something different from a hundred and twelve comments and four attachments. Tick what should go. For a document leaving the organisation, most people tick nearly everything except bookmarks, which help readers, and links they want to keep working. For a document going to a colleague, perhaps only earlier versions and document details.

Sanitise document

Sanitise removes the lot in one step. It's the right choice when you want certainty and don't need any of the extras, for instance a final copy for publication or disclosure. It's also the quickest.

In a routine with other tools

Hidden information fits into a sequence. Redact first, so the visible information is dealt with properly. Then remove hidden information or sanitise, so nothing survives in the background. Then, if needed, password protect the result. Remove hidden information and Sanitise are both steps that Actions can run, and the built-in action Prepare for distribution exists for exactly this kind of job, so you can process a whole folder the same way.

Run the check for unsafe redactions too if anything was hidden by covering rather than redacting. And if you want to read or set the document details yourself rather than remove them, Document properties and the XMP window are the place.

Things to bear in mind

Removing things is permanent in the saved copy. Keep your working file and save the cleaned version under a new name, so you still have your comments, attachments and history for your own use.

Look at the result once. Open the cleaned file, check the pages still read as they should, and look at Document properties to confirm the details are as you intended.

Doing this offline in PDF by Zaweba means the whole document, hidden parts included, stays on your PC while you decide what goes out with it.