if it's ok To send Zip then try this way

 String fileNameStor_zip = Environment.getExternalStorageDirectory() +"/" + fileName +".zip";String[] path = { your 1st pdf  File Path, your 2nd pdf  File Path};Compress compress = new Compress(path, fileNameStor_zip);compress.zip();URI =  Uri.parse("file://" + fileNameStor_zip);

Provide your Gmail Intent

intent.putExtra(Intent.EXTRA_STREAM, URI);