How to check out documents in SharePoint (read only mode)
If
you need to edit a document and want to be assured nobody else can edit the
same document in that time, it is recommended you Check Out the
document.
When
you check out a file from a library on a Microsoft SharePoint site, not only is
the time of editing exclusive to you, but nobody can see the changes you have
made to a document, until you check in the document upon completion. This gives
you the reassurance that you can proofread your changes, before granting others
access to the new updated copy.
1) Check a
file out
i) Navigate
to the library and hover over the document you want to check out.
ii) Hover
over the item you want to check out, and then click the tick box that appears
to the left to select it.
iii) Click
on the Files tab in the ribbon and click on the Check Out command
in the Open & Check Out group.
iv) The
document will be marked as Checked Out with a green arrow icon. If the Check
Out command is not available, the file may already be checked out to you or to
someone else, or you may not have the rights to check out and edit the
document.

2) Check a
file back in:
The
procedure for checking-in a file can be done in a number of ways. The most
common method is to check in the file, in the same way we have shown previously
to check out a file. Then the Ribbon command will show Check In, in
place of the Check Out command.