Android Question PDF FILE PROVIDER B4X

Have a look here. Download the example from the last post. It is easy to understand.
Other solution:
If your SDK level is below 30, you have access to the download folder, where the file is downloaded normally when transferred via FTP. You can copy it from there and put it to the working directory of your app. Good idea is to delete it then from the download folder. Then you can do whatever you want with that file.

Edit:
You can delete the class module of the example and simply put a hook at the FILEPROVIDER library in the libraries list of B4A, it is now an internal library. Same with the starter service, when not needed. For that you have to define the defined variables in the starter in your main project and change the "starter" locations in the main program.
For starting the PDF, I would put it's name on a button, which turns to green if the pdf-file exists at the place you defined for. If the file is there, the button click opens a new activity and loads your PDF.