As of print-o-matic version 2.0.1 the ability to use class to target a print element in external print triggers has been added. Basically it works the same as using the data-print_target attribute but instead uses a unique classname in the format of printtarget-<target_id>.
Create a target element. The element below is a div with an id of ‘my_print_target’:
<div id="my_print_target">This is the print target wrapped in a div with an element of 'my_print_target' as explained above</div>
Add an external trigger using the new class-trigger method. We’ll use a simple button like so:
<button id="my_print_button" class="printomatic printtarget-#my_print_target">Print Trigger</button>
Like in the original example, we need to add the hidden print trigger using a print-me shortcode with the same id as our external trigger and a printstyle=”external” attribute:
[print-me id="my_print_button" printstyle="external"/]