This is a PDF of the Apple II Redbook, the original reference manual for the Apple II from 1978. But it is more than just a PDF scan of an original; this is a digitally edited version that recreates the original look of the Redbook, but fixes the poorly printed parts of it to look as if it were printed with modern technology, rather than what was available in those early days.
Back in 2008, Gerry Doire created this and asked me to share it on the Apple II History web site. It has not changed in the last 15 years until Gary Graham took a look at it. He found typos in the 2008 version, and fixed the fonts to be more consistent with the original book.
This is still a work in progress, but Mr. Graham asked me to post this corrected version of the PDF, and some further improvements are still planned.