If we create a campaing to new leads/clients that we resend every time we get a new contact, it updates the original stat of the campaing or it creates a new stat?
I imagine that it creates a new stat. Is it posible join all these stats so we have a unique stat of the "New Leads/Clients" Campaing?
Every campaign is treated completely unique (even if the content and name is the same) so you will get a new report.
You can't join them, but you can use the compare campaigns option which will let you compare the stats across multiple campaigns.
A couple of ideas for the Compare functionality within the Reporting section.
1) It would be great if you can 'Filter' results (by keyword & date range) before selecting which campaigns to compare.
2) Export the Compare Campaign Result as a PDF (as per the single campaign reports)