Sometimes, currency formats will have a negative on the right side instead of the left.
In this case, you can go to PDF2XL Options > Format, and place a checkmark in the box labled "Move right side negative to left".
After that, make sure to mark your column format as "Currency" (or "Number").
If the preview still doesn't move the negative signs to the left, make sure you have deselected "Preview sizes, colors" on the preview pane toolbar.
Your converted document should place these cells in the format that is specific to your machine's regional settings.