Is there any changes that have occurred with invoices being attached as pdf files when emailing a customer?

Hello, kevinamis.

So far, there aren't any recent changes on how we send invoices attached as a PDF file. I'm willing to help you out some more regarding the emailed transactions. 

If your customers are seeing a different format with the online delivery, you'll want to tweak the settings in QuickBooks Online. Here's how: 

1. Click the Gear icon, then choose Account and settings. 
2. Go to the Sales tab. 
3. Expand the Online delivery section.
4. Change or tweak the options.
5. Click Save, then Done. 

Also, you might want to check your email messages if your customers are seeing different messages:

1. In the Sales tab again, expand the Messages section.
2. Add or edit the messages and their settings.
3. Once done, click Save. 

After checking either of the settings, send your invoices to your customers again. 

Though, I'd like to dive a little deeper regarding your concern. What are the changes did you see on the emailed invoices? Are your customers receiving any error messages when viewing the PDF file? More details would definitely help me address your issue properly. 

In the meantime, you'll want to check these articles out if you need help running sales reports, managing expenses or your customers. Go to our QuickBooks Online general help page for the topics, then look for an article. 

If you'd like to add other questions, please post them in the Comment section below. Happy to provide assistance again. Looking forward to your reply.