Change gutter setting

ID CS6 Windows

I imported a 1400+ page PDF into an InDesign document and set the gutter to 4.2333 mm. I want to change the gutter setting to 0. I went to Object | Text Frame Options and reset the gutter but the document did not move. In Layout | Margins and Columns, the gutter is also set to 0 now.

The gutter is still too big. How can I change the gutter setting?

TIA

Guy