An attachment is any kind of file that you want customers to be able to download before they purchase. For instance, you can post a .pdf of a user manual, or a video of a product demonstration.
Follow these steps to add an attachment to a product:
Go to the product’s page (Commerce → Catalog → select product), click on the Attachments tab and then the Add button in the upper-right to display the Add Attachment form. Click Select File to upload a file or to select one from the documents and media repository. Set a priority to control the order in which attachments are published on a page (lower numbers come first).
If you want to associate the attachment with a specific product variant, select one from the Options section of the Add Attachment form. (Variants are available to choose from only if a product has options designated as SKU contributors. See Options for details).
If you want the attachment to be displayed on the product page for a limited period of time, specify display and expiration dates in the Schedule section at the bottom of the form.