If you are working with PC documents, the system requires a working directory in which it can place the PC files created. This working directory must not be write protected.
Please make sure that a directory is specified in your SAP icon (File / Properties) under 'Working directory', which is not write protected.
You can only create and edit PC documents if you are working on a PC which has the required PC application. The system considers the application to be there if there is a valid entry for it in the PC register.