Including your logo on invoices is a great way to make them stand out. QuickBooks Online gives you the flexibility to add and edit logos on your invoices, estimates, or sales receipts. Making sure the logo size stays the same on your sales forms is essential. I'll be happy to share more on this.
After adding your logo to a sales form in QuickBooks Online, you're able to preview the PDF format to make sure everything looks right. The logo size in that previewed form should be the same as the size you get after creating or downloading your invoice. If this isn't the case, it could be due to a browser issue. Temporary internet files that accumulate in your browser can sometimes cause bugs in the software. To ensure your app or browser is running the program as designed, I recommend following the troubleshooting steps in this article: Clear cache and cookies to fix issues when using QuickBooks Online
You can also navigate in a private browser or use a different browser to eliminate any probability of a browser issue. Check out this article for compatible browsers with QuickBooks Online: System requirements for QuickBooks Online, Accountant, and QuickBooks Self-Employed
I hope this helps! Feel free to reach out if you need anything else!