(How) can I change multiple file names in a folder?

Yes you can. Open up Automator, and put in these actions:

Then run the workflow select the Folder of the scanned images, it will rename each sequentially.

Let me know if this has worked for you.

Hey man, no problem.

There are several sites you can look at that will give you a good idea on how to use Automator, such as:

Mac 101: Automator

Automatedworkflows.com tips and videos

(This is the site where I learned everything really, and this site also provides 3rd party actions that have greately helped me with better workflows)

Automator.us videos

Good luck man.

Thanks for posting this. I had everything but the "Get Folder Contents" and couldn't figure out what I was doing wrong. This worked perfectly. Saving a screen shot of the script as I'll probably space out the sequence by the next time I need it.

Glad I could help you.