pdf files and hidden text

[unhappycamper]

A thread was posted this morning in GD about the DOJ putting terraist manuals online.

The thread:
http://www.democraticunderground.com/discuss/duboard.php?az=view_all&address=104x4209170

The link to the DOJ web site:
http://www.usdoj.gov/ag/trainingmanual.htm

I opened the second link on the site using Adobe Reader 7.0.1. As I was mousing around the document, the reader tells me there's hidden text in the document. The reader appears not to have any tools to view the text.

My questions:
What does the hidden text say? Is it a digital fingerprint gone awry?

[charlie]

1. The text says the same thing

as what you're looking at on the screen.

The pages of the manual are scanned documents. Think of them as something akin to photographs. You can't do things like a text search on an image, even if it's a depiction of words. So when the Acrobat document is rendered, you can choose to have an OCR scan done on it. This creates a separate hidden cache of the text in the file, which is actually what you're using if you do a search, or copy and paste, etc.

[unhappycamper]

2. Thanks. Perhaps my tin foil hat was on too tight. n/t