from an existing PDF document thanks to the
<a href="https://www.setasign.com/products/fpdi/about/" target="_blank">FPDI</a> extension.
Then you can add some content to them.
</li>

<li id='q18'>
<p><b>18.</b> <span class='question'>I'd like to make a search engine in PHP and index PDF files. Can I do it with FPDF?</span></p>
No. But a GPL C utility does exist, pdftotext, which is able to extract the textual content from a PDF.
It's provided with the <a href="https://www.xpdfreader.com" target="_blank">Xpdf