<apex:page standardController="Opportunity" showHeader="false" renderAs="pdf">
<h2 style="font-family: sans-serif; text-align: center;">My PDF</h2>
<p><strong>Soci&eacute;t&eacute; : </strong>{!Opportunity.Account.Name}<br />
    <strong>Nom : </strong>{!Opportunity.Amount}<br />
    <strong>Pr&eacute;nom : </strong>{!Opportunity.Amount}<br />
    <strong>Adresse : </strong>adresse</p>
</apex:page>

• Have a button on my Opportunity page, "Generate PDF"
• On click, open an iframe over the same page, that displays the PDF (from the Visualforce page)
• Have two buttons on this iframe: Save // Cancel
• If I click save, it saves the PDF as a File, related to the current record