For a Reorder with New Files, you can make changes to any of your order specifications except for the binding type (for multi-page products such as Booklets and Catalogs).
For an Exact Repeat Reorder, you can change your order specifications except for the size, binding, number of pages, or any other design aspects determined by your original files.
If your Reorder was originally designed in the Online Design Tool, then you cannot make changes to the size, binding, number of pages, or any other design aspects determined by the original design. These aspects are locked in any Online Design Tool order.