You can import 3D annotations along with model geometry into Inventor with a STEP 242 file format.
If you're in Inventor 2019.1 or newer the option to import PMI-3D annotation data is available:
When opening a Step file, in the Import dialog box select 'Graphical PMI' to import 3D annotations:
If the option isn't available(greyed out) the Step file was either exported without 3D annotations and/or wasn't exported as a Step 242 file:
If the original file has 3D annotations and the 'Graphical PMI' selection is not available in Inventor, check the source software for an option to include them and the option to choose the Step 242 file format.
In some software when exporting to a Step file, in addition to choosing the 242 file format, you also have to choose to include existing 3D Annotations in the export. Otherwise the file is exported to a Step 242 file format without any of its 3D annotations.
In Inventor, when you export to Step 242 format, 3D annotations are automatically included.
In the Save dialog box select 'Options':
Choose to export as a STEP 242 format in the 'STEP File Save As Options' dialog box:
3D annotations will automatically be included in the export.