How to remove those red-box links in pdf verison of books?

[hajime]

Hello, I downloaded the pdf version of a book. In the Table of Contents, each section is highlighted by a box in red. When I clicked in the box, it jumps to the corresponding section. Similarly, within the text, when a section is referred (e.g. There is a box in red surrounding 3.9 in the text "In Section 3.9, we used "). Although this is helpful, I want to print out the book and such boxes look ugly. Can I make those red-boxes invisible? In the worse case, removing the hyper-link is ok. Thanks