You can change the orientation of the certificate by making the following alteration in tcpdf/config/tcpdf_config.php
To find this in your WordPress dashboard go to Plugins > Editor.
Select LearnDash LMS from the dropdown list.
Then press CTRL + F (Windows) or CMD + F (mac) to open the Find bar and copy this in: sfwd-lms/tcpdf/tcpdf.php and select the highlighted text.
Next do the same and copy in: sfwd-lms/tcpdf/config/tcpdf_config.php
You should see a caution note saying “Editing this code is highly discouraged. Proceed with caution.” – select Proceed, again select CTRL + F or CMD + F then paste in: PDF_PAGE_ORIENTATION
Now change the ‘L’
define (‘PDF_PAGE_ORIENTATION’, ‘L’);
define (‘PDF_PAGE_ORIENTATION’, ‘P’);
Finally, select Update file. Remember you will need to change the design to suit the new orientation.