You can increase the VM arguments, on %PUBLISHER_INSTALL_DIR%\publisher.ini, like:
The value to set the Xmx size depends on the specifications of the system you are working on. If this is not enough, you could try to increase again the Xmx value.
If during your work, the "Out of Memory" Error dialog box appears, change the java heap size and the MaxPermSize directly in this dialog box.
In the Xmx field, change the number of heap size '600' to a larger heap size in megabytes.
You can also change the java heap size in the magicdraw.properties file, in the line: