
Hi @prithavi
If you are only looking to open the documents in read only mode you can use Preview Graph API . This POST /users/{userId}/drive/items/{itemId}/preview
Graph API which returns "getUrl" in response that you can use to Preview(read) that file.
To Protect an excel file(making it read only) using Graph API, you can use WorksheetProtection Graph API.
As per my knowledge this Protect feature is not yet available for other files using Graph API. Since this feature/functionality is presently not available, you can submit a feature request idea using this support link, which will be monitored by Microsoft team and make the enhancements to Microsoft Graph APIs. I will also upvote for you.
Hope this helps.
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