java.lang.SecurityException: Permission Denial: opening provider androidx.core.content.FileProvider

Question

So I've been making these 2 apps and I want app 1 to be able to send pdf files to app 2. They're both signed with different keys as app 1 should be usable by any other apps as well.

The way I want it to work is as follows. App 2 sends a startActivityForResult to app 1 with an intent including a Uri with a file from App 2s fileprovider. Then app 1 should take the Uri and write the pdf onto the file provided by app 2. Then going back to app 2 the file should be written onto the file owned by app 2 in the first place.

Put simply the app 2 should provide a file where app 1 should write the pdf.

So I have it all set up like that but when trying to access the file to write to it, I get the java.lang.SecurityException: Permission Denial: opening provider androidx.core.content.FileProvider error message.

Full Error Message: Permission Denial: opening provider androidx.core.content.FileProvider from ProcessRecord{511cc8 14209:com.eureka.documentscanner/u0a159} (pid=14209, uid=10159) that is not exported from UID 10155

Code to copy the pdf's:

//This method is called once the app has selected the right pdf file and wants to return back to app 2.
    private void writeToSharedFile(){
        Intent StartingIntent = getIntent();

        //Get the shared file (the file to write to from app 2).
        Uri sharedFileUri = StartingIntent.getParcelableExtra(Intent.EXTRA_STREAM);

        //Get the file that I need to write into the shared file.
        Uri fileToWrite = Uri.fromFile(scanResult.pdfFile);

        //Write the file into the shared file.
        copyPDFs(fileToWrite,sharedFileUri);
    }


    private void copyPDFs(Uri from, Uri to){
        ParcelFileDescriptor pfdTo = null;
        FileOutputStream out = null;
        ParcelFileDescriptor pfdFrom = null;
        FileInputStream in = null;
        ContentResolver cr = context.getContentResolver();
        final String WRITE_ACCESS = "w";
        final String READ_ACCESS = "r";

        try {
            pfdTo = cr.openFileDescriptor(to, WRITE_ACCESS);
            out = new FileOutputStream(pfdTo.getFileDescriptor());

            pfdFrom = cr.openFileDescriptor(from, READ_ACCESS);
            in = new FileInputStream(pfdFrom.getFileDescriptor());

            //Reads from the input stream and writes the data to the output stream.
            int n;
            while ((n = in.read()) != -1) {
                out.write(n);
            }
        } catch (SecurityException e){
            e.printStackTrace();
        } catch (IOException e) {
            e.printStackTrace();
        }
        finally {
            // Let the document provider know you're done by closing the stream.
            if (out != null) {
                try {
                    out.close();
                } catch (IOException e) {
                    e.printStackTrace();
                }
            }

            if (in != null) {
                try {
                    in.close();
                } catch (IOException e) {
                    e.printStackTrace();
                }
            }

            if (pfdTo != null) {
                try {
                    pfdTo.close();
                } catch (IOException e) {
                    e.printStackTrace();
                }
            }

            if (pfdFrom != null) {
                try {
                    pfdFrom.close();
                } catch (IOException e) {
                    e.printStackTrace();
                }
            }
        } //Close the Streams and Descriptors.
    }

The security exception is always thrown on the pfdTo = cr.openFileDescriptor(to, WRITE_ACCESS); line.

I'm 100% sure there is read and write access on the intent used to start the activity for result, and that there is read and write permissions granted on the external storage.

Any suggestions or help would be appreciated.