How to implement custom fonts in TCPDF
// convert TTF font to TCPDF format and store it on the fonts folder
$fontname = TCPDF_FONTS::addTTFfont('/path-to-font/FreeSerifItalic.ttf', 'TrueTypeUnicode', '', 96);
// use the font
$pdf->SetFont($fontname, '', 14, '', false);