Is it possible to set up a folder so that every new file we add can be edited by a group of people, rather than just the original uploader?
Yes, this can be done. We currently don't provide that setting as the default everywhere in webCafé for important reasons. For example, students would not have editing rights to the posted course documents uploaded by faculty.
First look into whether you have edit access rights to a folder (if you created it or are shown as the "owner," you definitely already do). For example, if this is a private project folder for a team in the course, project team members would have edit access rights to the folder provided that the folder was made private when set up. Here's how to check:
If you do have editing access, e-mail or alert the group to propose that the folder be changed to default to everyone having edit access. (Or you could even create a Poll to decide it). Once the group's consensus has been reached, go back into the Access Control for the folder as described in the bullet point above. Then:
From that point forward, newly uploaded documents will be editable by the same people who have edit rights to the folder.
Note that this won't change the setting on documents that are already there -- as part of the process, the current "owners" of existing documents could make this same change on each pre-existing file individually. You could bring up the need for that at the time you propose changing a folder's setting.