With the Premium Templates customizer #
If you’re using the Premium Templates extension (part of our PDF Invoices & Packing Slips Bundle), you don’t have to create a custom template or use filters to apply custom styles, simply enter them in the Custom Styles box at the bottom of the Customizer tab of the settings:

With the free version #
If you want to change the styles of the WooCommerce PDF Invoices & Packing Slips, there are two ways to do this. You can create a custom template and simply edit the styles.css file.
Alternatively, if the changes you want to make are only small, you can also add your styles by using a filter in your themes functions.php. For example, to change the text and background color of the table header to black on white with a black border underneath:
add_action( 'wpo_wcpdf_custom_styles', 'wpo_wcpdf_custom_styles', 10, 2 );
function wpo_wcpdf_custom_styles ( $document_type, $document ) {
?>
.order-details thead th {
color: black; /* this is the text color of the header row */
background-color: white;
border: 0 0 2pt 0;
border-color: black;
}
<?php
}or to change the height of the logo from the default 3cm to 2cm:
add_action( 'wpo_wcpdf_custom_styles', 'wpo_wcpdf_custom_styles', 10, 2 );
function wpo_wcpdf_custom_styles ( $document_type, $document ) {
?>
td.header img {
max-height: 2cm;
width: auto;
}
<?php
}