I use Vista and I can edit standard fields in the details pane. However, although custom fields show up in explorer, they don't show up in the details pane.
Do they show in the file properties dialog box, full details pane?
Have you configured the details pane items to make these fields visible?
Also, make sure you are using the last 2.0.1 version. There is a related bug in previous versions.
Even so, it would take to much time to edit the fields of all those PDF files one by one.
In Windows Explorer you can select more than one file, and edit the property in all at the same time. Obvious only useful if you want to add the same field content to all.
If you need more complex metadata edit functionality, you can code a
MyScrits script, and run it from the explorer file context menu.