How can I cover a column in a Kami doc?

I have a document that I have used Kami to split and merge. Now in that merged doc there are some columns that I don’t want visible. I did not create the doc, so I can’t edit it, but I was hoping someone had figured out a way to just cover the columns. We tried highlighting in white (still shows) and creating a text box and filling it in white (text box is too small and when we enter to make it larger the box disappears!) Has anyone had a similar problem and come up with a solution?