I've come to ensure you'll able to view attachments in another tab, Tom MK.

We can modify your browser settings to allow and view PDF attachments or documents in a new tab. If you're using the Google Chrome browser, let's follow the steps below.

Here's how:

1. Go to the three-dot icon on the upper right of your browser.
2. Select Settings, then click Privacy and Security.
3. Click on the Site settings section and select Additional content settings under the Content tab.
4. Choose PDF documents and click Open PDFs in Chrome.

Additionally, if you're using a Microsoft Edge browser, here are the steps to modify its settings. 

Here's how:

1. Go to the three-dot icon on the upper right of your browser.
2. Select Settings, then click Cookies and site permissions from the left menu.
3. Locate and choose the PDF documents tab.
4. Click the PDF view settings to enable this feature in your browser.

All these procedures mentioned above are some of the troubleshooting steps that you may utilize to help you resolve the issue. 

I've added this guide to assist you in attaching transaction documents to each of your vendor and customer profiles: Add or delete attachments in QuickBooks Online.

Feel free to get back in this thread if you have any additional questions about pdf attachments. We'll be right here, willing to assist you. Take care and have a good one!