I am trying to overwrite the core AbstractPdf.php from
vendor/magento/module-sales/Model/order/PDF/AbstractPdf.php
To
app/design/frontend/vendor/projecta/Magento_Sales/Model/order/PDF/AbstractPdf.php
I did flush the cache after, but seems still using the core file, am I missing something? do I need to run some script to make this override works? I did search from any where over the internet, still not clear when I should do. Please help
Thanks!