Hi - so what is it that you are trying to accomplish? The conditional columns are not included in the PDF. And the column width for the PDF is defined in percentage of the available space. So I assume what you need is for the remaining columns, i.e. those that are included, to fill up the available space, however they don't because even though the conditional columns are not shown, they still use up space. Unfortunately there is currently no way to conditionally set the column width, or update the column width based on conditions. You could try your own custom report layout, or use the print APIs for export, and conditionally use different report layouts.
I'll take a note though to see if we can improve the logic using the built-in report layouts to be a bit smarter about use of space when columns are conditionally excluded.