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How to remove hidden information using Acrobat X

Learn how to protect PDF by removing hidden content such as links, actions, and JavaScript.

By October 10, 2010

 



In this tutorial, learn how to protect PDF by removing hidden content such as links, actions, and JavaScript.

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How to remove hidden information using Acrobat X

Annamarie LukesOctober 10, 2010

Previous versions of Acrobat contained a capability called "Examine Document".

In Acrobat X this has been renamed to "Remove Hidden Information" to more accurately describe what it does.

Some of the types of information that can be hidden and removed with the Remove Hidden Information tool are metadata, attachments, comments, form fields and digital signatures, deleted or cropped content, overlapping objects and now in Acrobat X also JavaScripts, links and actions.

There are many reasons why you might want to remove hidden information from a PDF - for example if you need to comply with regulations like the Health Insurance Portability & Accountability Act, the U.S.

Privacy Act, or for court filings.

If you are about to publish a PDF online, you'll probably want to remove any personal information like who created the document or when it was created.

If you have been inserting snarky comments on a PDF, you'll definitely want to remove those before the PDF goes out for wider distribution.

Now let's take a look at how to remove hidden information from a PDF.

First you select Tools and then you select Protection.

Move down near the bottom of the Protection panel where it says Hidden Information and select Remove Hidden Information.

The Remove Hidden Information panel opens on the left and shows you the results.

If you twirl down any of the arrows you can see all the different items that are going to be removed.

The hidden information that Acrobat found in this PDF is a lot of metadata and then two items of deleted or cropped content.

If you want to get a closer look at exactly what is in the metadata that's going to be removed, you can just select Show Preview and it will show you.

So in this case I can see that it had the author name, the title and I may or may not want to have that included in this PDF.

I am going to cancel out of this now and go back over to the Remove Hidden Information panel.

If I decide that it's okay to leave the metadata in, I can deselect this and then it will not remove that information but for right now let's select it and I will hit Remove.

Acrobat then tells me what else it's going to remove from this document and I select OK.

Notice that even though Acrobat tells you it is done removing the selected items that the changes are not applied until you save the document.

Don't worry - if you try to close this PDF right now without saving, Acrobat will prompt you to save it first.

The Remove Hidden Information tool is efficient and lets you see exactly what you're going to remove, but if you know that you always want to remove hidden information you can go to Preferences, select Documents and then down here where it says Hidden Information, you can select Remove Hidden Information when closing document or Remove Hidden Information when sending document by email.

That way it automatically happens; you don't even have to use the tool within Acrobat.

Another way to automate the removal of hidden information in Acrobat is to use the Action Wizard.

You can create your own Action or you can use an Action that comes with Acrobat X, Publish Sensitive Documents.

This action allows you to mark for redaction, then remove hidden information, and then reduce file size.

So it's a quick way to get through multiple processes.

For ultimate efficiency in removing hidden information from a PDF, you will want to use the bar of soap tool - which is known formally as the Sanitize Document tool.

When I select Sanitize Document, Acrobat displays a list that shows me everything that is going to be removed once I save the document.

So when I press OK, it prompts me for a place to save it.

I will give it a prefix and click Save.

Now with my newly-sanitized file open, let's take a look at Remove Hidden Information, see what it finds and it tells us "No potentially sensitive information was found." Acrobat has done its job.


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