You can use MBS FileMaker Plugin and try the DynaPDF commands.
So you would load the PDF into our plugin, use the DynaPDF.WebLink command to add weblinks.
If you don't have coordinates, the DynaPDF.FindText function may help.
Maybe you first get familiar with our plugin by downloading and playing with examples?
Love the plugin. Had fun with the ability to get info on all of the USB drives on a computer.
The help file you provide from 3rd party is excellent and FileMaker should use it rather than the html one.