I’m curious, but did you have any specific type of app in mind that you wanted to open the pdf file with? Or was you hoping that the available options that might appear would automatically be filtered based on the apps which “could” open pdf files?
If it’s the later, then I don’t know how that could be accomplished, not sure a site would have that type of capability to interact with any iPhone apps.
When I mentioned before about the floating groups, I was thinking more along the lines of “visually”.
I’ll be back online tomorrow so will have a look.