I was looking for a solution to produce an exact official form in PDF format with the field values entered by a user in a web form. Here is what I found:

Create a PDF Form using Acrobat Writer. Note down the field names.

Get form values from user using a web form.

Generate the FDF(http://www.verypdf.com/pdfform/fdf.htm) file by passing the values along with the field names.

function createFDF($file,$info){
    $data="%FDF-1.2\n%âãÏÓ\n1 0 obj\n<< \n/FDF << /Fields [ ";
    foreach($info as $field => $val){
        if(is_array($val)){
            $data.='<</T('.$field.')/V[';
            foreach($val as $opt)
                $data.='('.trim($opt).')';
            $data.=']>>';
        }else{
            $data.='<</T('.$field.')/V('.trim($val).')>>';
        }
    }
    $data.="] \n/F (".$file.") /ID [ <".md5(time()).">\n] >>".
        " \n>> \nendobj\ntrailer\n".
        "<<\n/Root 1 0 R \n\n>>\n%%EOF\n";
    return $data;
}
?>

Use pdftk(http://www.pdflabs.com) to fill out the PDF form using the FDF file.

header('Content-type: application/pdf');
header('Content-Disposition: attachment; filename="Download.pdf"');
passthru("pdftk file.pdf fill_form data.fdf output - flatten");
exit;