Welcome to the Community, info-musiciansof. I'm here to assist you with aligning your checks correctly when printing in QuickBooks Online.
To begin with, you need to reset the default value of the Vertical and Horizontal fields to Zero (0). After that, you can fine-tune alignment once again.
Also, when you select the print option in QuickBooks, your default print dialog box opens. Depending on your setup, this might be the print dialog from your browser, Adobe Acrobat, or your printer’s driver. Adjusting the scale or page size will vary based on your printing experience.
If the issue persists, update your Adobe Reader and set it as your default PDF viewer. For more details, you can visit this article on how to set up your print settings so you can print checks: Configure your print settings for printing checks in QuickBooks Online.
Lastly, I've got some resources you might need for additional information on how to fix print alignment for preprinted checks in QuickBooks Online.
Fill me in if you have additional questions when printing checks in QBO. I'm always here to help. Take care, and have a lovely day.