Read-only access on files shared in Personal chat needed instead of automatic change permissions

Hi everybody. Here is my question and case. In my mission to get MS Teams in pole-position for collaboration between teams and leaders, I had a talk with a senior manager. He had an understandable reason why he was not completely hooked to working with Teams (only). Here is why: He must write a lot of decision-making documents. His documents are stored on his personal One-drive. When he shares a link to this document in a chat with a colleague, he also gives write permission to the original document of his. That makes him unsecure of always having the right and unchanged document available when needed. Therefore he works around this issue with sending a PDF or the real document as an attachment 😞 in the mail to his peers. How can he share documents (links) without giving change permissions also?