How to save an AutoCAD drawing to a previous or older file format

Issue:

How to save a drawing in AutoCAD to an older file format to allow prior versions of AutoCAD to open the file instead of receiving the following message: 
 

Open Drawing - Incompatible Version
The drawing file could not be opened because it was created with a more recent version of AutoCAD. 

Causes:

The file was created or saved in a more recent version of AutoCAD in a newer DWG format. See the article  AutoCAD drawing file formats for the AutoCAD file format change history and compatibilities.

Solution:

The Save As dialog window in AutoCAD allows selecting different drawing versions:

1. Click the "Save As" button on the Quick Access Toolbar in AutoCAD or type SAVEAS on the command line.
2. It is suggested to change the name of the file to prevent overwriting the original.
3. Choose the appropriate file format version under the "Files of Type" drop-down menu.
4. Save the file.

If a file has been received in a newer format that cannot be opened by the version of AutoCAD currently installed (hence receiving the above "incompatible version message"), ask the sender to resave it to the older format that can be used or download and install the latest version of  DWG TrueView (free Autodesk file viewing software) and use its DWG Convert feature to convert the drawing:

1. Create a copy of the drawing file to be converted.
2. Launch DWG TrueView.
3. Click the application menu in the upper-left and choose DWG Convert (or pick it on the ribbon if you have a file open).
4. Add the file(s) in the Files Tree list (click the green plus Add Files button).
5. Choose the appropriate file format version.
6. Click Convert.

For AutoCAD for Mac, use AutoCAD Mobile (TrueView is not available for the Mac OS):

1. Log in to AutoCAD Mobile.
2. Upload the drawing and then view it.
3. Click the "Download" button.
4. Choose DWG and the appropriate file format version.