Download the file : fmx-pdf-test

This is a demo/test app using FMX PDFium library. It contains full source, the windows exe and the Android apk files. If you want to compile it then you do need to download PDFium.

The trial version is Here

Finally, there is no OpenDialog on Android. I have made available four folders that you can select from, to grab the pdf file. If it doesn't find any files there, it shows you the path, so you can copy a pdf there with a file manager. I use X-plore.