We can mark a file as read-only from command line too. Command for this is given below.
attrib +R filename
attrib +R example.doc
The above command will set the read only attribute for the file file.doc and user will not be able to do modifications to the file.
To check if a file has read only attribute set, you can check by running attrib command on the file.
D:\data\> attrib example.doc A R D:\data\example.doc
Recursively set read-only attribute for all files in the directory
attrib /S +R