Hi! It’s possible that there are PHP errors written in the PDF data (resulting from your PHP settings or WP_DEBUG or rather than the ‘Debug output’ option in the plugin), I’ve seen this with another user too. Try opening the PDF in a plain text editor to see if this is indeed the case. Here’s what I found in the other case:
Warning: file_exists(): open_basedir restriction in effect. File(/tmp/log.htm) is not within the allowed path(s): ([...]) in /wp-content/plugins/woocommerce-pdf-invoices-packing-slips/vendor/dompdf/dompdf/src/Dompdf.php on line 699
Warning: is_writable(): open_basedir restriction in effect. File(/tmp) is not within the allowed path(s): ([...]) in /wp-content/plugins/woocommerce-pdf-invoices-packing-slips/vendor/dompdf/dompdf/src/Dompdf.php on line 699
Warning: is_writable(): open_basedir restriction in effect. File(/tmp/log.htm) is not within the allowed path(s): ([...]) in /wp-content/plugins/woocommerce-pdf-invoices-packing-slips/vendor/dompdf/dompdf/src/Dompdf.php on line 704
Warning: is_writable(): open_basedir restriction in effect. File(/tmp/log.htm) is not within the allowed path(s): ([...]) in /wp-content/plugins/woocommerce-pdf-invoices-packing-slips/vendor/dompdf/dompdf/src/Dompdf.php on line 850
This particular error will be fixed with the next update. If you don’t mind editing plugin files yourself, check this commit:
explicitly set log file for dompdf (otherwise defaults to system tmp folder)
Let me know what you find!