Hi and welcome to the forum!
What do you mean exactly? It can be locked if the system thinks that the file is already in use. In this case, just delete the .lock... file that should be in the same folder than the file.
If the document is read-only, click the Edit icon in the main toolbar. It can be linked to the drive where you've saved it (rights issue). We don't have enough details to give a clear answer.
AOO 4.0.1 on Windows 7 and Xubuntu 13.10 (Saucy Salamander)