Hi,
Are you asking why or how to do that on pdf template?
For how see this link:
https://wiki.dolibarr.org/index.php/Setup_Other
Go to: Home ► Setup -> Other Setup
The below are what you need:
MAIN_GENERATE_PROPOSALS_WITH_PICTURE ► Include the first image of the product into the line of the generated PDF for customer proposals.
MAIN_GENERATE_INVOICES_WITH_PICTURE ► Include the first image of the product into the line of the generated PDF for customer invoices.
MAIN_GENERATE_SUPPLIER_PROPOSAL_WITH_PICTURE ► Include the first image of the product into the line of the generated PDF for supplier proposals ► (v5.0.3+)
