We are using Outlook email. We are using the tab browser technique. Starting at the Outlook home page, there are several panes. When you open an email with a PDF, then click on the attachment, it opens in like a pop-up. At the top, there are two buttons, a download and print. When you click on the print the new window event fires, and we create a second tap. The window is blank. I have a shortcut that will copy that tab's URL. If I copy and paste it into a Chrome browser, you can see the document with Chrome looking print UI. I can send you the link. I am not sure how long it is available, and/or because of cookies, you may not be able to access it. I am somewhat struggling to describe it, I was hoping trying to print a Google document might be some sort of clue. Looking at a Devtool on Chrome, I see a lot of type script, initator *.js, with status of 200.

Here is the link, I cut out some where the ellipses are (...)
https://attachments.office.net/mail/pdfprint.html?id=AAMkADU4NWM1NTc1LT (...) ANARY=X-OWA-CANARY_cookie_is_null_or_empty&owa=outlook.office.com&scriptVer=20250502003.07&clientId=xxxxxxxxxxxxxxxxx&routingKey=Stxxx%2540braums.com&animation=true

Let me add another note... I just emailed it to my personal email, which gets forwarded to Gmail, so using the Gmail browser, when I clicked on the printer icon, it showed in a new tab and is able to be printed.
I wonder what Outlook is doing differently?