How do I reorder files in a file list? Not sort. Reorder

Attachments:

If you mean using the /attachments macro to display the attachments for a page, you can edit the macro and change the sort order (ascending or descending).

You cannot reorder them, unless you give them alphabetically ordered names to achieve the correct order (sort by name), or upload them in the correct order (sort by createddate).

Pages:

If you mean changing the order of the pages in the space, you can grab the page name in the menu on the left hand side and just drag them to reorder:

It will even give you a nice message when the page has moved.

If you mean something else, please describe what a file list is and add a screenshot of where it resides.