How to create PDF different than A4 - portrait

I'm migrating from another application to Joomla / OS property and i've run into an issue: my client needs to create A5 landscape sized PDF's to create flyers from the properties. I've activated TCPDF and saw some configuration options in the files under this folder: components/com_os_property/helpers/npdf/_class/
However, i could not manage to get it done.

Who will point me in the right direction?

Would it - ultimately - be possible to create a selectbox with layouts and sizes before creating the pdf?

Hi Loco Creations,
If you open file: components > com_osproperty > classes > listing.php, you can find this line:
$html2pdf = new HTML2PDF('P', 'A4', 'en', true, 'UTF-8');
And you can try to change A4 by A5.
In fact, i am not sure it will work, but you can try it
Thanks
Dam