In Revit 2012, you can create a selection and isolate, hide, or apply graphic setting for the elements in the selection. You can also load the selection later to make the elements selected again, and set "Comment" parameter, or copy/paste aligned to other levels, etc.
Here is an example:
1. Select the beam, column, floor on the second floor plan.
2. Click Manage tab>Selection panel>Save.
3. In the Save Selection dialog, enter the name "2nd Floor structure".
5.Click View tab>Graphics panel>Visibility/Graphics.
6.In the Visibility/Graphics dialog, under the Filters tab, click Add
7. In Add Filters dialog, select "2nd Floor structure", click OK.
8. Set Lines and Patterns under Projection/Surface, click OK.
You will see the beam, column, floor display using the defined line color, weight, etc.
9. Click Manage tab>Selection panel>Load.
10. In the Retrieve Filters dialog, select "2nd Floor structure".
You will see the beam, column, slab on the second floor plan are selected at once.
11. In Properties dialog, set parameter "Comment" value as "2nd Structure".
12. Click Modify|Multi-Select tab>Clipboard panel>Paste>Aligned to Selected levels, select Level 3, click OK
You will see all the beam, column, floor on Level 2 is copied to level 3.
13. Open a 3D view, and follow step 9 and 10, click "Isolate Element" in view control bar, then only the second floor structure elements shown in 3D view, and you can export your second floor structure to dwg.
Tip: In step 11, set parameter "Comment" value, you might use it as a Find Item criterion after exporting Revit model to Navisworks.