tcpdf - start with existing PDF document

You want to use FPDI.

There's some example code here.

I have tried the free version of FPDI but does not support PDF version 1.5 or higher.

If someone else is looking for a free solution I have used TCPDI. You can find it on github https://github.com/pauln/tcpdi If you are using composer, you can find some fork for composer too. Just search tcpdi on github.

Once you add it to your project, the code is quite simple. It is an extension of TCPDF so all your previous code keep working

This is a snippet from my code. I used it to save a copy of the privacy policy (a static pdf) with the user name and agreement date on each page footer.

// Create new PDF document
$pdf = new TCPDI(PDF_PAGE_ORIENTATION, PDF_UNIT, PDF_PAGE_FORMAT, true, 'UTF-8', false);
...
// Add the pages from the source file.
$pagecount = $pdf->setSourceFile($policyPdfPath);
for ($i = 1; $i <= $pagecount; $i++) {
    $tplidx = $pdf->importPage($i);
    $pdf->AddPage();
    $pdf->useTemplate($tplidx);
    // Add agreement text in document footer
    $pdf->SetXY(15,282);
    $pdf->Cell(180, 5, "Documento approvato da {$fullName} il {$date}", 0, 0, 'C');
}
// Send PDF on output
$pdf->Output(FOLDER_PATH . DIRECTORY_SEPARATOR . "{$userId}.pdf", 'F');