Unexpected change in fonts for all pdf documents

On opening a pdf file in Acrobat Pro 9, a pop-up appeared about accessibility options. Wanting to work quickly I clicked on what seemed the obvious option, and found that the font had changed in the document I was proofing. The same happens with other documents. How do I reset Acrobat to open documents in the proper font? I have made sure it is supposed to open in 'local fonts', and I need to see documents in their original fonts for proofing purposes. Please help.