1) Share a folder on another computer or a Network Attached Storage device using CIFS (e.g. "\\COMPUTER_NAME\shared_folder")
2) Using Windows Explorer, go to "C:\Users\user_name\", right-click on "My Documents" or "Documents" and select "Properties".
3) In "Documents Properties", open tab "Location", then click on button "Move..."
4) In "Select Destination", select the Network resource (remote CIFS share). No need to transfer the contents of your current "My Documents" folder.
5) Install ARMA 3 and Subscribe to any number of Missions via Steam Workshop.
6) Open ARMA 3 and attempt to launch one of these missions. The missions are listed but you will be unable to view the cover-image of each mission and ARMA 3 will fail to launch the missions, with a misleading error message indicating that there is not enough disk space.
7) Launch an ARMA 3 Campaign, save the progress, exit ARMA 3 and try to reload the Campaign. The options RESUME and REVERT will be missing. You will only have the option of starting the campaign from the beginning.