title: How to download a pdf file in react native?
body: <p>I am building an app with React Native and Expo, for Android and iOS. I am trying to let the user download a PDF file when clicking on a button.
  It's a couple of days that I'm working on it and I find tow following packages:</p>
  
  <ol>
  <li>react-native-fetch-blob/rn-fetch-blob</li>
  <li>react-native-fs <br/></li>
  </ol>
  
  <p>the first one raises :<br/> 
  <strong>undefined is not an object (evaluating 'RNFetchBlob.DocumentDir')</strong> <br/>
  and for second the error is:<br/>
  <strong>undefined is not an object (evaluating 'RNFSManager.RNFSFileTypeRegular')</strong> <br/><br/>
  I've previously tested the npm link , Yarn eject , restart packager and some other workarounds form GitHub and stackoverFlow but my problem is not solved yet.<br/></p>
  
  <p>any help is highly appreciated Thanks.</p>