I get PDF invoices from a supplier. What happens if they are more than one page with the amounts on the last page? Can I mark both scans as being from the same receipt?

Hello there, @lucaviggiani17.

You can attach your documents to an invoice in QuickBooks Online.

Here's how:

1. Go to the +New icon, then click Invoice.
2. From the Customer drop-down arrow, select a customer. Make sure all of their info is correct, especially their email address.
3.  On the Invoice page, click Attachments.
4. Browse the file you want to add, then click Open to add.
5. Make sure to remove the checkmark in the Attach to email box.
6. Fill in the other necessary fields.
7. Hit Save and close, once done.

For more information about the file types that you can attach, check this article: Attachments in QuickBooks Online. 

For future reference, this article can be handy on email or print multiple invoices and sales forms.

Keep me posted in the comments if you have any other questions. Always got your back here in the Community.