Display external pdf in modal not external

There is quite a few older posts about NOT having a PDF display in modal.

But in my situation this is not the case.

As I understand it modal happens if you using a file stored within the database.

However because of limitations, we store the PDF on our server.

We have used text equations to build up the physical address of the file.

But when we display it via clickable link it goes full screen and KNACK has no way of controlling the browser so DOWNLOAD etc is still active.

So my question is how can we display the PDF in a popup (whether it be knack modal or an external api of some sort) so that we can display the pdf but not allow it to be downloaded.

Application is a digital museum concept of WW2 memorabilia and items

Cheers