Unfortunately, I am unaware of any other solution for embedded analytics (i.e. actually tracking the engagement within the PDF)
We don't produce a lot of PDFs, and the ones we do are generally coming from our Editorial teams / other sources and provided as a resource on our articles... as such, trying to get proper embedded tracking into those files (from mostly non-technical people) hasn't been a priority for us... we just do the simple "download pdf" metrics.
I assume that this is a similar challenge for you, how do you get the people who are authoring these PDFs to properly embed tracking, and I don't really have an answer.
The only other option I can think of (and bear in mind that this is completely untested and may not work at all) would be to embed a non-JS tracking pixel / hardcoded image inside the PDF... this wouldn't give you a lot of granularity, it would probably just track once upon opening when the pixel is loaded as an image resource.... (this will also inflate your Visits and Unique Visitors numbers as there will be no proper User Identification or cookies to remember anything about the user)
If you are interesting in investigating that option, here is how to hardcode an image request:
https://experienceleague.adobe.com/docs/analytics/implementation/other/hardcoded.html?lang=en
