You can share your diagram with others even if they don't own SmartDraw by sending them a link. To get the link, click the Share button in the upper right corner of the UI.
From the drop-down menu, select Copy Link.
You'll get a dialog where you can choose whether the person you send the link to can just View or both View and Edit your diagram.
Pick the option you want and click on Copy Link to copy the link to your clipboard. You can now email that or put it in a chat program like Slack or Teams.
Related articles:
Learn how to share diagrams stored on OneDrive.
Learn how to share diagrams stored on Google Drive.