Hi there,
You'll want to adjust the spacing of your invoice from your Word document before importing it to your QuickBooks Online (QBO) account.
Once done making these changes, import it again to your QBO account. Here's an article you can read for more details in importing custom form styles in your QBO: Import custom form styles for invoices or estimates.
You might also want to check this link that provides detailed information on how you can print your forms for window envelopes.
Do get back to us in case you have other concerns or questions. I'll be around to help. Stay safe.