But i am using my own layout(custom one), Howcan i apply it to this one?

<?xml version="1.0" encoding="UTF-8"?>
<odoo>
    <template id="account_commercial_custom_layout">

        <div class="header" style="margin-bottom:50px;  page-break-inside: avoid;">
            <div class="row" style="display: flex; width:100%;">

                <table class="table" style="width: 100%; margin-bottom:5px; border-bottom:none;">
                    <!-- Row 1: Totals -->
                    <tr>
                        <td style="width: 30%; text-align: right;">
                            <div style="text-align:left;">
                                <img src="\vkd_invoice_report\static\logo.jpg"
                                     style="max-height: 100px; margin-bottom:5px"
                                     alt="Company Logo"/>
                            </div>
                            <div style="font-size: 14px; line-height: 1; text-align:left;">
                                <strong>REGISTERED ADDRESS:</strong>
                                <div t-field="o.company_id.partner_id"
                                     t-options='{"widget":"contact","fields":["address","name"],"no-maker":True }'/>
                            </div>
                        </td>
                        <td style="width: 40%;">
                            <div style="font-size: 14px; line-height: 1; text-align:right; margin-top: 50px;">

                                <strong t-field="o.company_id.name"/>
                                <br/>
                                <span t-field="o.company_id.street"/>
                                <br/>
                                <span t-if="o.company_id.street2" t-field="o.company_id.street2"/>
                                <br/>
                                <span t-field="o.company_id.city"/>
                                <span t-if="o.company_id.state_id">,
                                    <span t-field="o.company_id.state_id.name"/>
                                </span>
                                <span t-field="o.company_id.zip"/>
                                <br/>
                                <span t-if="o.company_id.country_id" t-field="o.company_id.country_id.name"/>
                            </div>
                        </td>
                        <td style="width: 30%; text-align: right;">
                            <div style="font-size:18px; font-weight:bold;  color: #d9534f; text-transform: uppercase; text-align:center; margin-top: 80px">
                                COMMERCIAL INVOICE
                            </div>
                        </td>
                    </tr>

                </table>
            </div>
        </div>
        <div class="article" style="position:relative;">
            <!-- Watermark -->
            <div t-if="report_type == 'pdf'"
                 style="position: fixed; top: 30px; left: 0; width: 100%; -webkit-transform: rotate(-30deg); transform:rotate(-30deg); text-align: center; z-index: 0; opacity: 0.15; pointer-events: none;">
                <span style="font-size:9em; color:#FF7F50; font-weight:bold; display:inline-block;">
                    Invoice
                </span>
            </div>
            <t t-raw="0"/>
        </div>
        <!--footer section-->
        <div style="margin-bottom:5px;" class="footer">
            <hr style="border:none; border-top: 3px solid #000; margin: 5px 0;"/>
            <div style="width:100%; font-size: 20px; margin-bottom:5px;">
                <div t-if="report_type == 'pdf'" class="text-muted">
                    Page:
                    <span class="page"/>
                    of
                    <span class="topage"/>
                    <span style="float:right; font-size:20px">
                        <strong>Printed:</strong>
                        <t t-esc="datetime.datetime.now().strftime('%Y-%m-%d')"/>
                    </span>
                </div>
            </div>
        </div>
        <!--footer section-->
    </template>
</odoo>

Hi,

To print the header/footer only on the first/last page, you can use the OCA module.

* https://odoo-community.org/shop/report-qweb-element-page-visibility-2192

After installing the module, use the first-page or last-page class.

Header

<div class="header">

    <div class="first-page">

        <div class="row">

            <img t-if="company.custom_report_header"

                 t-att-src="image_data_uri(company.custom_report_header)"

                 alt="Logo" width="100%"/>

        </div>

    </div>

</div>

Footer.

<div class="footer o_standard_footer">

    <div class="last-page">

        <div style="width: 100%;">

             <img t-if="company.custom_report_footer"

             t-att-src="image_data_uri(company.custom_report_footer)"

             alt="Logo" width="100%"/>

          </div>

      </div

</div>

Hope it helps