Hi Kevin,
Try using Deeplink Module. You can create a deep link microflow which gets called when you click on hyperlink. It shows the page you want in new tab.
For more details, please refer Deep link Module Documentation.
This might help you:
https://stackoverflow.com/questions/2947404/how-to-open-link-to-pdf-file-in-new-tab-using-html
But when you Google your issue it seems more something related how PDF files work.
Good luck.