Hi there, @VonGecko.

Let me provide you with troubleshooting steps so you'll be able to preview an estimate before sending it to your customer. 

I suggest accessing your QuickBooks account via a private or incognito window to check if this is a browser-related issue. At times, data stored for a long period causes unusual behavior in the browser. Doing so helps disable the cache from saving your browsing data.

You can use either of these keyboard shortcuts:

• For Google Chrome browser: Ctrl + Shift + N
• For Mozilla Firefox browser: Ctrl + Shift + P
• For Safari browser: Command + Option + P

If it works, go back to the regular browser and clear its cache. This is done to clear them out periodically to prevent and fix web issues.

Once done, I suggest updating the Adobe Reader/Acrobat. The majority of printing or previewing PDF issues in QuickBooks Online can be resolved by updating Adobe Reader/Acrobat to the latest version or by repairing your Adobe installation. You can check the Adobe website for detailed instructions.

Please refer to this article to see steps on how you can customize, attach files, and email sales forms to your customer within QuickBooks Online: Customized invoices, estimates, and sales receipts in QuickBooks Online.

Please feel free to leave a comment below If you have further concerns regarding estimates and invoices. I'm always here to help. Have a good one!