Oh, I see the problem. You clicked the "View e-book version" link. That goes to the publisher's store. As far as I know they never had a PDF, just a special web version.

Click the book's title in the paragraph above that, where it says this:

> Agarwal, Anant, and Jeffrey H. Lang. Foundations of Analog and Digital Electronic Circuits. San Mateo, CA: Morgan Kaufmann Publishers, Elsevier, July 2005. ISBN: 9781558607354.

That takes you to a PDF.

Sorry for not being more specific. I didn't even notice the "View e-book version" as I only went to the site to remind myself of the name of the book, saw the title was a link, and clicked it. Then I thought "Why is MIT linking to a pirate copy of a book from one of their own professors?", and did a little Googling to get some backstory.