the only know i know to handle this read/edit permission from office is by protecting the document and those options have different reasons
if you are sharing from sharepoint
if you are giving read permissions from SharePoint this means the user cannot modify the published version, but if they download the document, then they will be able to modify it, yet they wont be able to publish it into SharePoint.
if you are protecting the document in office:
this means your READ users CAN'T modify no matter how the document until the protection is lifted. but, if you didn't add the correct permissions on the SharePoint site then they would be able to overwrite the document with whatever other document they want if it has the same name.
Remember SharePoint is to protect the shared versions,
MS is to protect the document itself.
-- Additional note,
as Password protected documents remove the read capability of any service to read its contents as the information is encrypted, any protected document won't display its metadata on sharepoint.