Topic is fairly old but figured I could help @yveslens out.
I fixed this issue by changing the following lines:
In /wp-content/plugins/woocommerce-pdf-print/tpdf/font/unifont/dejavusanscondensed.mtx.php
$tttfile='..../DejaVuSansCondensed.ttf';
to
$ttffile = __DIR__ . '/DejaVuSansCondensed.ttf';
Same exact thing for dejavusanscondensed-bold.mtx.php and dejavuserifcondensed-italic.mtx.php
In my case, we inherited a client who had recently migrated their website. The .mtx.php files are apparently internal cache files and the $ttffile variable was cached with the old absolute path to the .ttf files. Using __DIR__ outputs the correct path.
