How to set permissions to edit/save files copied from a Win 7 PC

I'm working on a project where I have to generate a series of screengrabs on a PC and transfer them to my MacPro via the network for onward tranmission via email but some need to be edited first in Photoshop.

If I'm just forwarding them via email with no changes there's no problem, but when I need to edit them in Photoshop I can't save unless I go to Get Info for the file concerned, unlock Sharing & Permissions (which requires my administrator password) and then change the 'everyone' drop-down setting from 'Read only' to 'Read & Write', then re-lock and close Get Info.

The default permissions for the PC files as they arrive over the network are:

nobody Read & Write

staff Read only

everyone Read only

I have dozens and possibly a hundred or more of these to do, so having to re-set Permissions every time is a major pain and waste of time.

Is there something I can change either on the Mac or the PC (which is running Windows 7) so that I can just edit and save these files without all this hassle?

Thanks,

Michael