Thanks for the reply. I had seen the thread but it didn't seem to answer my query, I have since revisited it and done some more tests.

I have saved the project with reorganisation and although it complains the project seems to be identical so I am presuming that there were no active PDM elements in the project and will proceed with the modification.

However, it would still be nice to get an answer to the original question or maybe even a slightly wider question.

If a program uses packages not available (such as PDM, or SCL) is it safe to edit the LAD or STL files, can they be edited without messing up the entire program?

If anybody has an answer that would be great.

Chris

Description of Error:

The project may contain objects that can only be processed with an software package that is not installed or a newer version of the software package is required.

To Correct or Avoid Error:

Please install the required software package.
or
Make a copy of your project in the SIMATIC Manager [with File> Save As and the "With reorganization (slow)" option]. While the copy is being made, objects are deleted in the destination project if they belong to uninstalled software packages. The error message is then no longer displayed when you work with the copy of the project.