How to open the attachment in another window?
WooCommerce Product Attachment Plugin lets your buyers use the download button to open the attachment in the same window or open the attachment in another window.
For this you must choose the right radio button in the Settings > Setting section related to the same.
If your attachment is a web link and you do not want the buyer to go to another page, leaving your store, it is better to let him/her open the attachment in a new tab.
In other cases where you have attachments to be downloaded, you should let buyers use the download button. It helps you ensure a good shopping experience.