Looking over your screenshots in the "Help screenshots_1.docx" document from your original post, it looks like you are calling GenerateEForm with the "pdf1" as both your step page and your TargetEFormPage. As the "pdf1" page is used as the TargetEFormPage, I suspect that this page is of the class Code-Pega-eForm. When "pdf1" is used as the step page as well, that means your step page context is also Code-Pega-eForm and the system will look for your Rule-Map-eForm rule in that class. As you're Rule-Map-eForm rule is in SAE-Myapplic-Work-Practice, the system won't find it.
I believe you should be able to avoid this error by creating a page of the class SAE-Myapplic-Work-Practice , and use that newly created page as your step page when you call GenerateEForm. You'll still want to use your "pdf1" page as the TargetEFormPage, but swapping to a step page with the same class as your Map eForm rule will likely avoid the error.
You don't show your pages and classes tab on the activity. Do you define the page pdf1 in your class SAE-Amapplic-Work-Practice? It's possible that the page context is throwing things off. I haven't had a moment to dig into your trace, so I could be way off, but that might be a quick place to look. The error is pretty clear that it's looking in the class Code-Pega-eForm. Another thing you could try might be to create your Map eForm rule in that class to see if it gets picked up.