Easy fix is to put the pdf file in your public folder and set href="resume.pdf".

You can also create a folder named resume in your public and put the pdf file inside your resume folder.

<a href="/resume/resume.pdf" download><strong>Download my Resume!</strong></a>

This answer is by @hexebioc

fetchFile(){
   axios({
            url: `/someurl/thefiles/${this.props.file.id}`,
            method: "GET",
            headers: headers,
            responseType: "blob" // important
        }).then(response => {
            const url = window.URL.createObjectURL(new Blob([response.data]));
            const link = document.createElement("a");
            link.href = url;
            link.setAttribute(
                "download",
                `${this.props.file.name}.${this.props.file.mime}`
            );
            document.body.appendChild(link);
            link.click();
        });


}

render(){

  return(
      
      <button onClick={this.fetchFile}> Download file </button>
    
  )

}

<script src="https://cdnjs.cloudflare.com/ajax/libs/react/16.6.3/umd/react.production.min.js"></script>
<script src="https://cdnjs.cloudflare.com/ajax/libs/react-dom/16.6.3/umd/react-dom.production.min.js"></script>

Try this

<Link to="/files/manual.pdf" target="_blank" download>Download</Link>

Where /files/manual.pdf is inside your public folder

Figured it out, posting in case this finds useful to someone else... If you are on android trying to download then open a file and it opens blank you most likely don't have permissions. This is regardless of which file viewing and downloading tools you use. https://github.com/joltup/rn-fetch-blob/issues/483#issuecomment-761763626

Solution I used:

RNFS.downloadFile(options)
  .promise.then(()=> PermissionsAndroid.requestMultiple([
    PermissionsAndroid.PERMISSIONS.READ_EXTERNAL_STORAGE,
    PermissionsAndroid.PERMISSIONS.WRITE_EXTERNAL_STORAGE,
  ]))
  .then((result) => {
    const isGranted = result[PermissionsAndroid.PERMISSIONS.READ_EXTERNAL_STORAGE] === 'granted' 
    && result[PermissionsAndroid.PERMISSIONS.WRITE_EXTERNAL_STORAGE] === 'granted';

    isGranted ? FileViewer.open(filePath, {showOpenWithDialog: true, showAppsSuggestions: true}) : console.log('Declined')})
  .then(() => {
    console.log('File should have opened');
  })

tldr; fetch the file from the url, store it as a local Blob, inject a link element into the DOM, and click it to download the Blob

I had a PDF file that was stored in S3 behind a Cloudfront URL. I wanted the user to be able to click a button and immediately initiate a download without popping open a new tab with a PDF preview. Generally, if a file is hosted at a URL that has a different domain that the site the user is currently on, immediate downloads are blocked by many browsers for user security reasons. If you use this solution, do not initiate the file download unless a user clicks on a button to intentionally download.

In order to get by this, I needed to fetch the file from the URL getting around any CORS policies to save a local Blob that would then be the source of the downloaded file. In the code below, make sure you swap in your own fileURL, Content-Type, and FileName.

fetch('https://cors-anywhere.herokuapp.com/' + fileURL, {
    method: 'GET',
    headers: {
      'Content-Type': 'application/pdf',
    },
  })
  .then((response) => response.blob())
  .then((blob) => {
    // Create blob link to download
    const url = window.URL.createObjectURL(blob);

    const link = document.createElement('a');
    link.href = url;
    link.setAttribute(
      'download',
      `FileName.pdf`,
    );

    // Append to html link element page
    document.body.appendChild(link);

    // Start download
    link.click();

    // Clean up and remove the link
    link.parentNode.removeChild(link);
  });

This solution references solutions to getting a blob from a URL and using a CORS proxy.

Update As of January 31st, 2021, the cors-anywhere demo hosted on Heroku servers will only allow limited use for testing purposes and cannot be used for production applications. You will have to host your own cors-anywhere server by following cors-anywhere or cors-server.