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PDF readers are implementing security measures to protect you from malicious PDFs. I'll look at what to do when that interferes with a PDF's content.

In your documents, you have words highlighted in blue to click for more info. When I click on them, I receive a message: “In Safe Mode, this document does not allow connection to your site. If you want to enable this function, please check the Trust Manager preference to disable safe reading.”

How do I do this?

PDF format has become the latest target for malware. As it turns out, there are assorted vulnerabilities in various PDF readers, as well as in the very definition of PDF format itself. Hackers are creating malicious PDF documents in an attempt to infect your computer with malicious software.

The net result is that PDF readers have begun implementing various security measures to allow you to read PDF documents in safety.

"Safe Mode" is one such measure in Foxit Reader.

It's easy to turn off and I'll show you how. I'll also discuss the threat that it's protecting you from.

The Problem

The problem that we're facing is a very simple one. Much like web pages, PDF documents can include links that go to other web pages on the internet. When you click such a link, the PDF reader may inform you that it's disallowed:

Foxit Reader Security Block

To quote:

In safe reading mode, this document does not allow connection to:
http://go.ask-leo.com/procmon

If you want to enable this function, please check the Trust Manager preferences to disable safe reading mode.

That's after an attempt to click one of the links in my Maintaining XP guide.

Disable this "safe reading mode"? We can do that.

Disabling safe reading

In Foxit Reader, click the Tools menu, the Preferences menu item, and then the Trust Manager sub-item in the left column:

Foxit Reader Trust manager

As you can see, the Trust Manager has exactly one option:

Foxit Reader Trust Manager - the one option

Un-check Enable Safe Reading Mode, and click OK. Now, when you click a link, you'll get a simple warning that will allow you to proceed:

Foxit Link Warning

Click "Yes" and your web browser will open on the link shown.

What am I getting myself into?

Disabling something called "safe" reading mode implies that you're doing something that's not safe.

Kinda sorta, but not really.

As you can see when safe mode was disabled, you weren't prevented from clicking the link, but you were warned, with a clear indication of the destination of the link. Rather than having your PDF reader trust no one, it's now up to you to know who to trust.

The "problem" is that PDF files do more than open pages in your web browser.

Foxit's own words around the safe reading mode option:

Foxit recommends that you check this option for controlling unauthorized actions and data transmissions; including URL connections, launching external files, and running Javascript functions to efficiently avoid attacks from malicious documents.

As I've said, PDF is a powerful format. With that comes risk. PDF documents can:

  • Make URL connections - which means opening up your web browser to a web page. Unless you have the opportunity to examine the URL first, a malicious document could take you to a malicious web site.

  • Launch external files - which means clicking a link in a PDF document could run a program on your machine. Perhaps a malicious program, perhaps a standard program used in a malicious way.

  • Run Javascript - just like in your web browser, Javascript can be included in PDF documents and can be used for good ... or evil.

The fact is that Foxit's safe reading mode is, perhaps, a bit of overkill as it disables all of these at once. That's unfortunate in my opinion, because allowing clickable links is quite common, whereas running programs or Javascript, while possible, is rarely seen in actually PDF documents. I'd love to see an option to ONLY allow clicks - with a preview - to http: URLs and leave the other items disabled.

Next Steps

If you regularly receive documents from sources that you trust and you have the ability to evaluate any suspicious actions if the reader warns you about them, then I'd feel safe disabling this option. As you can see, it's required to enable clickable links in PDF documents.

If you're interested in learning a little more about PDF format and why it's so popular, have a look at Just what is PDF format, how do I view it, and why do people use it?

Video

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Transcript

Hello, everyone! This is Leo Notenboom for askleo.net.

We're going to take a look at the trust manager in Foxit PDF Reader and get it out of the way when you want to click a link in a PDF document.

I'll open up a PDF document here in Foxit; I happen to already have it open on a page that has such a link. If we click on this link, Foxit will tell us we can't do it because the trust manager has put us into what they call 'safe reading mode'. Let's turn that off.

We'll find the trust manager in Tools -> Preferences -> Trust manager and we will uncheck 'Safe Reading Mode'. Click on 'Ok'. Now when we click on the link, we'll get one warning that we're about to go somewhere; since we trust the site, we'll go ahead and click 'Yes' and the site comes up.

That's it!

I'm Leo Notenboom for askleo.net.

Article C4967 - October 28, 2011 « »

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Leo Leo A. Notenboom has been playing with computers since he was required to take a programming class in 1976. An 18 year career as a programmer at Microsoft soon followed. After "retiring" in 2001, Leo started Ask Leo! in 2003 as a place for answers to common computer and technical questions. More about Leo.

Not what you needed?

3 Comments
Me
November 1, 2011 11:12 AM

Sometimes I wish there was a way to quickly toggle this without digging through the menus.

I agree. I was somewhat surprised at how buried this is.
Leo
02-Nov-2011
tom
December 27, 2011 2:58 PM

Hi,
I use Foxit-reader (v4.3.0) as an add-on in IE8 and Firefox 8, but cannot find how to access the preferences in the Foxit add-on to disable the safe-reading mode (Trust manager). Any idea how to find the preferences/trust-manager in the add-on?
Thanks in advance!
tom

Just run FoxIt from the start menu, and therein you'll see the options menu.
Leo
27-Dec-2011
Tom
December 10, 2012 7:41 AM

Open reader then hit control+K and that is the way to open preferences as it is not listed in tools!!

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