Here's the multiAdd to Cart code you'll need:

<a href="javascript:EJEJC_multiAdd(Array(
'https://www.e-junkie.com/ecom/gb.php?c=cart&ejc=2&cl=XXXXXX&i=YYYYYY',
'https://www.e-junkie.com/ecom/gb.php?c=cart&ejc=2&cl=XXXXXX&i=ZZZZZZ'
));" style="display: inline-block;background: #3da5d9 url(https://www.e-junkie.com/ej/images/newaddtocart.png) center/100px no-repeat;border: none;padding: 7px 55px;border-radius: 3px;box-shadow: 1px 2px 2px rgba(0,0,0,0.2);text-decoration:none;">&nbsp;</a>

Those example URLs shown in the 2nd and 3rd lines there will need to be replaced with the actual href= URLs from your Add to Cart button code2 for each item. You can add as many URLs as you want in the list, but note that all except the very last one need a comma after the closing quote at the end (as shown above).

This also depends on having at least one copy of our Cart Script code copied from your Cart button codes screen3 and pasted into the same page; this loads some javascript to display our cart as an overlay within your page, which also handles the multiAdd function.

pdf stamping for each item will still work with this, correct?

Yes, PDF Stamping will still work when using a multi-add button.