I downloaded a Costco Credit Card Reward Certificate, but when I try to print it, it is on the far right & partially cut off. I haven't found any way to correct that.

They should be able to scan it on your phone, and they usually mail the actual certificate to you as well. If you're still having an issue go to the help desk or call costco. the certificate is also made with a piece of paper that reacts to heat and I'm sure they use that to identify it's originality. That may be why your printer is having an issue

For printing you have to go to the settings for your printer. As many have suggested a screen shot of the barcode works too I usually do the self service checkout and use the barcode on their checkout scanner.

Take your receipt to the customer service desk

I would agree with talking to them at Costco. Go to the membership desk, they would most likely handle that.

Screen capture it and then print it if possible . Ie on windows using the snipping tool and paste into WordPad then print.

Speak to a representative.

Try minimizing a little bit see if it helps

Show the certificate on the phone when you go to Costco