snip.js

var appFilePath = Ti.Filesystem.resourcesDirectory + 'w4.pdf';
var appFile = Ti.Filesystem.getFile(appFilePath);
var tmpFile = undefined,
    newPath = undefined;

if (Ti.Filesystem.isExternalStoragePresent()) {
    tmpFile = Ti.Filesystem.createTempFile();
    newPath = tmpFile.nativePath + '.pdf';
    tmpFile.move(newPath);
    tmpFile = Ti.Filesystem.getFile(newPath);
    tmpFile.write(appFile.read());
} else {
    Ti.API.error('No external storage present');
}