How do you send a pdf to the system pdfviewer?

[Taifun]

@Michael_Secker

At the moment i copy the the desired pdf from the above mentioned dir to "/Documents" in Scope "shared" and use this location as datauri for activity starter.

If you want to use the activity starter, this is the way to go

@Michael_Secker

Also i cann't be shure not to overwrite an existing file in /Documents by accident.

You only can overwrite files, your app owns, see also Some basics on Android storage system
Also you first can check, if the file exists before overwriting

@Michael_Secker

So whats a better way?

Use an extension to view the pdf directly from ASD, see the extensions directory App Inventor Extensions | Pura Vida Apps

@Michael_Secker

Can i use a reachable system-temp-dir where the system does the cleanup?

You could copy the pdf always to the same target directory and use always the same filename

Taifun