“Nor were slaves used to build them - those that worked on the complex were well paid, fed, and cared for - it was an honor to work on them.†See Lehner, Hawass et al.
"... information didn't include the purpose of the pyramids?" No. No one know the answer as to the purpose of the pyramids at Giza. It is not information as in something written down, but rather a tracing of archaeological clues, designs and so on - too much to elaborate on here.
See: Egyptian Dawn
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Maybe you should check out some actual research. Here is a good article to start with. These are papyruses found a few years ago that are from the time of the actual building projects in Giza.