If you attach a document to the Global Equipment collection in the Equipment Library and decide that you want to remove it. You can't remove it from the Library form. You must open the data grid and delete it from there. All of the datagrids have a [-] button in the record navigator at the bottom left of the page.
1. Open the Equipment grid (or any other grid to which you have erroneously attached a document)
2. Expand the [+] button to the left of the record to expose the sub grids.
3. Select the Documents Collection tab.
4. Select the row that has the offending record.
5. Click the [-] button on the record navigator at the bottom left of the grid.
6. Save the grid.