Unfotunately, you cannot.
Once one personal edition modifies-reloads-saves a Qlik demo document, the embedded license is replaced by the "license"-identifier of that Personal Edition. All other personal editions will now regard it as an externally created document and will try to "recover" it. Sorry.
If you want to do real development using QlikView, you should buy one or more licenses. Qlik still offers local licenses that do not require you to buy a server. Personal Edition is for evaluation purposes only.