How do I change the color of all the text in a PDF?

Hi.

I have a large PDF, over 1000 pages. Some of the text is highlighted which makes it difficult to see on my preferred document background. In Acrobat XI how do I change the color of all the text in the document back to black please? Although solutions using any other software will be much appreciated too.

I searched this forum already, and the same question was asked back in 2007 when it appears the only solution was to use an expensive third party plugin.

Thanks.