As claimed in The Guardian.
A transcription of the document is apparently available on JSTOR here, the section "Pesquisa Del Comendador Francisco de Bobadilla".
Has the document been confirmed as genuine?
Skeptics Stack Exchange is a question and answer site for scientific skepticism. It only takes a minute to sign up.Sign up to join this community
The document was found in 2005 by archivist Isabel Aguirre in the General Archive of Simancas. So far, nobody has disputed its authenticity and a renown expert on Columbus, Consuelo Varela, published a book and several scientific publications on it.
TL;DR; Yes, the document is deemed authentic.
Disclaimer: the document being authentic and the events presented in it being true are, of course, two different things. The document was used in the trial against Columbus, and it was written by the main prosecutor of the case, Francisco de Bobadilla.
You can have a look at the book Varela & Aguirre wrote about this document and the general cause against Columbus here