I have never heard of adding a second Attachments column, and I don't think you can.

I would suggest using a naming convention to either prefix or suffix the file names so you can tell which work order they belong to.

Something like

    1_some file name.jpg
    1_some other file.jpg
    2_second work order file.jpg
    2_another file.jpg

or

    some file name_1.jpg
    some other file_1.jpg
    second work order file_2.jpg
    another file_2.jpg