Thanks for posting in the Community! Sharing is available for all account levels. If you share your document with a basic or free level user they will be able to open it. However if you have advanced shapes on the canvas or you are using pro-level features that basic-level users do not have access to they may face restrictions in their ability to edit the document. But they will be able to open it. Be sure to check out our Account Types article from our Help Center for more information.

Hope this helps! Happy Diagramming!