dompdf is an HTML to PDF converter included in Tiki
Since Tiki18, mPDF is the recommended PDF generator
Also: if you want to generate PDFs from a web-based slideshow, you should really upgrade to Tiki19 (the slideshow has been massively improved). dompdf has been completely removed.
dompdf
dompdf is an HTML to PDF converter
https://github.com/dompdf/dompdf
dompdf support was added in Tiki9 to export the Slideshow to PDF.