When you are using .set_pdfSettings() client-side method, you actually override the PDF settings of your RadClientExportManager. So if you set only fileName, the pageBreakSelector will no longer be in the settings of the RadClientExportManager. Here
you may find a screen-shot, showing this.
In your case, in order the multi-page functionality to work, you must use the following code:
is the class of the element on which you want to break the page.
You may find more information on Client-side programming in the following help article:
Hope this will be helpful.
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