Please share your code you are working on so that we can guide you.

this is my simple template

<t t-call="web.external_layout">

<div class="page">

<div class="oe_structure"/>

<h2>Call for Tenders</h2>

<h3>Products</h3>

<table class="table table-condensed">

<thead>

<tr>

<th><strong>Order Reference</strong></th>

<th><strong>Description</strong></th>

<th><strong>Vendor</strong></th>

<th><strong>Product</strong></th>

</tr>

</thead>

<tbody>

<td>

<span t-field="o.order_id"/>

</td>

<td>

<span t-field="o.name"/>

</td>

<td>

<span t-field="o.partner_id"/>

</td>

<td>

<span t-field="o.product_id"/>

</td>

</tbody>

</table>

<div class="oe_structure"/>

</div>

</t>

</t>

Now action

<report

string="Purchase Comparison"

id="action_report_purchase_tender"

model="purchase.order.line"

report_type="qweb-pdf"

name="purchase_tender_app.report_tender"

file="purchase_tender_app.report.report_tender"

print_report_name="'Tender - %s' % (object.name)"

/>

But it gives report of only one line at a time but i want all my lines in one report.

Thanks for replying