The last official act of Robert E. Lee as president of Lee university was sign a carte d'visit of himself for a young girl admirer who met him on the steps of the university as he was leaving for the day. Within hours, Lee had a stroke and didn't survive long.
What was the last thing FDR signed?
Supposedly JFK's last in-person signature was on a newspaper handed to him on the morning of his death by a member of the housekeeping crew at the hotel he was staying at. I think it later sold for for $80,000+.
What was the last document/autograph signed by Elvis Presely?
Compiling such a book I'm sure would require a herculean effort. Besides, how could you track down the person at the Ambassador Hotel for whom RFK quickly scribbled his autograph within minutes of being shot.