If you have enabled web access for a partner on this project and have allowed access to selections and change orders from the Settings > Partners page, he may be able to see certain files attached to change orders after you request approval with the "Save & Request Approval" button.
As you upload new files to your change orders, you can choose whether the files will be visible to your partners.
After you have requested approval, the files with a green partner icon (the picture of the 3 people) will be visible to your partners who have web access for the project. To hide a file, click on the "Hide" link next to the icon.