You can share a document only when you're in the single client view. You'll not see Publish to Portal in All clients view (that is if you see the Documents for all your clients)

1. In MYOB Practice, go to the client and click Documents in the top menu bar.
2. Select the document you want to share and click Publish to Portal.
3. In the Publish to portal window, make sure
   
   1. Signature required is unticked.
   2. Notify people is selected.
4. Click Next.
5. Click Add other contributors > Add contributor.
6. In the search box, search for a name or add a new contact.
7. After selecting the users or contributors you want to share the document with, click Done.
8. Complete other fields if required and select Publish and notify.
   The Share Document Name dialog appears. It shows who the document has already been shared with.
9. If you want to remove someone’s access,  click the remove () icon.
10. An icon will be displayed next to the selected document if it has been shared with one or more contributors. You can click the icon at any time to see who a document has been shared with. If no contributors were selected, the icon isn’t displayed.
11. Any users and contributors that you have selected to share the document with will receive an notification by email.