In its third generation now, the Amazon Kindle remains a popular e-book reader, letting readers wireless download and read books. The Kindle 3, as the third generation is known, uses E Ink Pearl technology rather than an LCD display, as some other e-book readers do. According to Amazon, E Ink Pearl makes for better contrast when reading books and as such does not require any adjustment because you can read the display in any light. However, because you can also read PDFs on your Kindle, you may occasionally need to adjust a PDF's contrast.
Open a PDF file you want to read by pressing the "Home" button and selecting the PDF you want to open.
Press the "Aa" button located next to the spacebar. A settings screen will open.
Select "Contrast" using the five-way controller, navigate to the desired contrast and select the setting. You can select "lightest," "lighter," "default," "darker" or "darkest." The contrast setting will stay in effect until the next time you change it.