With help from a dev at WordPress Questions I got this solved. In wp-content/plugins/cforms/cforms.php we added
require_once(dirname(__FILE__) . '/html2pdf/html2pdf.class.php');
which loaded all the necessary data from the folder html2pdf which has all the files based on code from html2pdf.fr
Further in the same file after $newcontent .= substr($content,$last); we have code to pdfy the code:
$pdfContent="<table width="560" border="0" cellspacing="1" cellpadding="2" bgcolor="#CCCCCC">";
for($i = 1; $i <= $field_count; $i++) {
if ( !$custom )
$field_stat = explode('$#$', $cformsSettings['form'.$no]['cforms'.$no.'_count_field_' . $i]);
else
$field_stat = explode('$#$', $customfields[$i-1]);
$field_name = $field_stat[0];
$field_type = $field_stat[1];
$field_required = $field_stat[2];
$field_emailcheck = $field_stat[3];
$field_clear = $field_stat[4];
$field_disabled = $field_stat[5];
$field_readonly = $field_stat[6];
if($field_type == 'fieldsetstart') {
$pdfContent.='<tr><td colspan="2"></td> </tr><tr><td align="left" colspan="2" valign="middle"><span style="width:100pxheight:30px;float:left">' . stripslashes(($field_name)) . '</span></td></tr><tr><td colspan="2"></td> </tr><tr><td colspan="2"></td> </tr><tr><td colspan="2"></td> </tr>' ;
}
else if($field_type =='textarea') {
$pdfContent.='<tr><td align="left" valign="middle"><span style="width:100pxheight:30px;float:left">' . stripslashes(($field_name)) . '</span></td><td valign="middle" bgcolor="#ffffff" align="left"><span style="width:300px;height:30px;float:left"><textarea cols="40" style="width:400px;height:100px;"></textarea></span></td></tr><tr><td colspan="2"></td> </tr>' ;
}
else{
$pdfContent.='<tr><td align="left" valign="middle"><span style="width:100pxheight:30px;float:left">' . stripslashes(($field_name)) . '</span></td><td valign="middle" bgcolor="#ffffff" align="left"><span style="width:300px;height:30px;float:left"><input type="text" style="width:350px;height:30px;"></span></td></tr><tr><td colspan="2"></td> </tr>' ;
}
and
$pdfContent.='</table>';
//echo $pdfContent;
try
{
$html2pdf = new HTML2PDF('P', 'A4', 'fr');
$html2pdf->writeHTML($pdfContent, isset($_GET['vuehtml']));
$html2pdf->Output(dirname(__FILE__) . '/html2pdf/pdf/form.pdf','F');
}
catch(HTML2PDF_exception $e) {
echo $e;
exit;
}