You can share documents with other users via sharing in ERPNext.
In addition to user and role permissions, you can also share a document with another user if you have sharing rights for that document. Note that, a shared document will be visible to the other user even if the document is restricted via User Permissions.
To share a document, open the document, click on the "+" icon under sharing and select the user with whom you want to share:
In the popup window, you can either select all users or one particular user.
Read, write, submit, and share access can be granted to the user for this document.