Before you can make changes to a document, you must first check it out.
To check-out a document
Open the Projects module.
Select an item.
Select the Documents tab.
Select a document, right-click and select Check Out.
In the Check Out dialog box, add comments. Select Mark the file as checked out, but do not download the file to replace the file with the copy you have on
your local computer when you check it back in.
Click OK.
Save the file to your local computer. (Opening the file directly can place the working
copy of the document in your temporary Internet files directory.)