Here is the step by step description.
- Open any drawing with version AutoCAD 2015 or later, then set the View ribbon tab current. This also works in verticals such as Civil 3D.
Select the View Ribbon Tab
- Locate the Model Viewports panel and left click on the words Viewport Configuration to activate the drop down selection list.
Accessing the Viewport Configuration drop down selection list.
- From the drop down selection list, left click on Two: Vertical (or any other option except Single) to view multiple viewports on the Model tab of your current drawing.
Select a viewport configuration with multiple viewports.
- With the multiple viewports visible, you can now hover your cursor over any of the adjoining lines between viewports, left click, hold, and drag to the desired location. When you get the line moved to the desired location, release the left mouse button.
You can also add viewports by using the + as the beginning point of the left click, hold, and drag location. By dragging an existing viewport near another viewport boundary you can delete an existing viewport. To see this in greater detail, I refer you to Greg Battin's AutoCAD Tips blog post titled AutoCAD 2015 Resize Model Space Viewports.