I've never tried to use the HTML front-end. Indeed, I may have misunderstood what it's all about, since I didn't really look at it.
I have, however, edited metadata using the command line interface.
It works roughly like this. Suppose the file whose metadata you want to edit is called "plato-republic.pdf"
First, you have to "dump" the metadata from the current .PDF into a textfile, with a command like:
pdftk plato-republic.pdf dump_data output plato-republic-metadata.txt
That should create a textfile called plato-republic-metadata.txt. Open it using a text editor.
You should find values in there like:
InfoKey: Title
InfoValue: The Republic
InfoKey: Author
InfoValue: Plato
InfoKey: Subject
InfoValue: Philosophy
Go ahead and change "The Republic" to whatever you want, and "Plato" to whatever you want... etc. Leave everythign else the same. (If a pair of InfoValue:/InfoKey: lines is missing for one of these tags, you can add them.) Save the file.
Now use another command line:
pdftk plato-republic.pdf update_info plato-republic-metadata.txt output plato-republic2.pdf
That should create a new .pdf with the revised metadata. Check it out. If it works, you can keep the new one and delete the old one.
Yeah,
major pain in the butt. I'm very thankful I have the Professional Version of Acrobat now; I used to do it this way.
Still, I think there may be other things out there too.
EDIT 1:
There's this:
http://www.versiontracker.com/dyn/moreinfo/macosx/30639
That might be command-line too, though.
EDIT 2:
AHA.... what about this?
http://www.sybrex.com/products/macgui/infomanager/