Supported order by
The plugin supports order by title, date and custom order in ascending or descending order.
title & date are the fields which you entered / selected when publish a PDF.
Every document has a system last modified meta but when upload in WordPress the meta will be ignored and only the date when you upload saved as "last modified" in WordPress.
BSK PDF Manager Pro now has the feature of save the system last modified meta when upload PDF by file input field.
Please make sure you use file input upload way ( not by WordPress Media Library or by FTP ) and checked the check box.
Set PDF custom order
In PDFs list view you may assign a number as order to specific PDF. The order would be saved by Ajax.