Use a PDF reader like Adobe Acrobat or Preview to highlight key passages and add digital sticky notes.

Here is a put-together feature profile of the textbook and how to access it.

You might wonder: Why use an older PDF like FHSST when Khan Academy and CK-12 exist?

Unlike traditional textbooks that cost hundreds of dollars, the FHSST books are released under the GNU Free Documentation License. This means you can legally download, print, and distribute them to an entire classroom for free.

: Detailed look at the circulatory, respiratory, and digestive systems.