A facility to duplicate objects (paragraphs, spreadsheet cells, images, etc) is present in most applications. FreeCAD is no exception. Document objects may be freely copied within a document or between documents using the Copy, Paste and Duplicate Selection commands.
Document objects may be linked to other objects (for example, a Pad feature is linked to it's Sketch, and a Fusion feature is linked to it's component objects). This means that some care must be exercised in selecting objects to copy.
If an object is selected without it's children, those children are not automatically duplicated by Copy/Paste or Duplicate Selection. In this case, the copied object may exhibit unexpected behaviour due to expected links not being present.
In general, recommended practice is to select all dependent objects when copying a parent object.
After the Copy/Paste operation, it may not be obvious where the new object(s) are located in the Document window. That is because the new object has the same Placement property as the original. Toggle the Visibility property (spacebar) to hide the original. Then use the Placement dialog to move the copy to it's correct position.
Like most things in FreeCAD, there are many ways of making a copy. For more ideas, look at: