This feature is in Run.
When searching for documents, users can select all of the documents by clicking the checkbox in the header row of the document list. Additionally, documents can be individually selected and unselected by clicking the checkbox in each respective row. The select-all box can also be used when no search has been run.
Importantly, this provides a simple method of selecting almost all of the results of a search for a mass actions (such as adding tags, batch printing, etc.).