The default settings of the certificate print off centered. It continued to have issues not being centered even with manipulating settings. There were trackers on this, however the client reported Remote Learner was able to put in a fix that we do not currently have. 

STEPS TO REPLICATE

1. Go to any course and create a certificate activity.

2. Print the default certificate and notice it slightly off center. 

3. Choose the letter type and either portrait or landscape will give a more noticeable off center layout.

When the Certificate activity is configured to "Certificate Type" = "Letter Embedded" or "Letter Non-Embedded", the PDF downloaded by the user should be in the US Letter size, 8.5 by 11 inches (215.9 mm x 279.4 mm).
ACTUAL RESULT: The PDF downloaded by the user is A4 (ISO 216) size, 8.3 by 11.7 inches (210 mm × 297 mm)

Note from client: 

Paper types in TCPDF are case sensitive.

Change
$pdf = new PDF($certificate->orientation, 'pt', 'Letter', true, 'UTF-8', false);

to

$pdf = new PDF($certificate->orientation, 'pt', 'LETTER', true, 'UTF-8', false);

at line 28 in the certificate definition (certificate.php)|