1. Add your content via the website builder

• On the e-commerce, edit the product page
• Add some blocks/text at the bottom of the page, and save

-> The content added is actually stored in an HTML field on product.template, which is not visible on the form view by default.

2. Export your products

• Go to the back-end, open the products catalog
• Select them all, or the products you need to update
• Export the products, check "I want to update data", and select the field "Description for the website" (technical name = website_description)
  
  

3. Import the products

• Copy/paste the value of the HTML field to the other products
• Import the file