Fermat's works were published by Tannery and Henry in four volumes, the last of which appeared in 1912.

An additional volume was edited by de Waard in 1922:

>Fermat, P. Oeuvres de Fermat: Suppl\'ement aux tomes I--IV. Documents in\'edits publi\'es avec notices sur les nouveaux manuscrits par M.V. De Waard 1922. 

I have the pdfs for Tannery's volumes but I can't find one for de Waard.  Does anyone have a pdf for de Waard and/or know where one can find one?