Hi,

add below line in your report tab,

    print_report_name = "(object.name+'.pdf')"
eg:

<report
        id = "report_custom"
        string = "Print pdf"
        model = "model_name"
        report_type = "qweb-pdf"
        file = "module_name.report_custom"
        name = "module_name.report_custom"
        paperformat = "module_name.paperformat_a4"
        print_report_name = "(object.name+'.pdf')"
/>

Thanks
Aswini iWesabe