Why does the PDF version of my invoice (custom template) look COMPLETELY DIFFERENT than the preview?

Why does the PDF version of my invoice (custom template) look COMPLETELY DIFFERENT than the preview?

The invoice that displays on screen, right before I click SEND, is beautiful.

The invoice that gets converted into PDF or emailed via the Send button -- much more simple.

Could it have something to do with the fact that I created custom HTML templates?  Why doesn't that show up as the preview, though?