Extract pages to separate pdf's (something wrong with loop?)

Please check following code.

Acrobat makes duplicates of the original file with all pages in each new generated files instead of the right extracted pages (example: filename_page_2.pdf must be page 2 of the original pdf).

Another question is that now when the script was running is that at the end of the batch Acrobat asks to save the original file

What am I doing wrong?

/* Extract Pages to Folder */

    var re = /.*\/|\.pdf$/ig;

    var filename = this.path.replace(re,"");
    var lastPage=this.numPages-1;

    {
        for ( var i = 0;  i < this.numPages; i++ )
        this.extractPages
         ({
            nStart: 0,
            nEnd: lastPage,
            cPath : filename + "_page_" + (i+1) + ".pdf"
        });
    };