How do I limit the number of versions per document in a document library? We'd like to do this to save space, as SharePoint stores a full copy of each version of a document in a library (so I've been told). Also, once implemented, what happens to the old versions beyond the threshold? For instance, if I have a file with 30 versions, and I implement a 10 version limit, do the oldest 20 versions get deleted?
you could write an Event Handler and attach it to your document library; when document versions count reach your custom limit, it's up to you decide what to do with previous versions.
EDIT: Sorry, there are a simpler way: go to your document library definition; below "General Settings", select "Versioning settings" and enter your version count limits in "Optionally limit the number of versions to retain".