All users can create unlimited copies of their projects. To create a project duplicate, click the copy button in the project summary bar, as shown below.

Making a copy will preserve all the values, geometries, and changes of the previous file, but in a new project so nothing has to be lost or redone.

Note: If you are missing the copy button on the project management page - it is like you have not completed any analysis (energy/daylight/load modeling). In this case, you will first have to complete the analysis and then create a copy of your project. The copy button appears only when the project has geometry associated with it, and has completed one of the analyses.