Mozilla pdf.js, How to I specify the filename for download?

Question

I pass the location of the php file that contains the following code as parameter to the viewer.html file and it is displayed correctly but when clicking the download button in the pdf viewer the document name is always document.pdf. This poses a problem because of how many mobile users will be downloading files only to discover that all of their files have the the name document.pdf and that they (for most mobile browsers) can't change the filename before downloading.

Do I have to pass some arbitrary parameter to the file or redirect to self with the filename appended?

<?php
$content = "a binary representation of my pdf";
header("Content-type: application/pdf");
header('Content-Transfer-Encoding: binary');
header('Content-Disposition: attachment; filename="someFile.pdf"');
echo $content;
?>

Answer 1

I've run into this same issue. From the pdf.js's viewer.js source:

function getPDFFileNameFromURL(url) {
  var reURI = /^(?:([^:]+:)?\/\/[^\/]+)?([^?#]*)(\?[^#]*)?(#.*)?$/;
  //            SCHEME      HOST         1.PATH  2.QUERY   3.REF
  // Pattern to get last matching NAME.pdf
  var reFilename = /[^\/?#=]+\.pdf\b(?!.*\.pdf\b)/i;
  var splitURI = reURI.exec(url);
  var suggestedFilename = reFilename.exec(splitURI[1]) ||
                           reFilename.exec(splitURI[2]) ||
                           reFilename.exec(splitURI[3]);
  if (suggestedFilename) {
    suggestedFilename = suggestedFilename[0];
    if (suggestedFilename.indexOf('%') != -1) {
      // URL-encoded %2Fpath%2Fto%2Ffile.pdf should be file.pdf
      try {
        suggestedFilename =
          reFilename.exec(decodeURIComponent(suggestedFilename))[0];
      } catch(e) { // Possible (extremely rare) errors:
        // URIError "Malformed URI", e.g. for "%AA.pdf"
        // TypeError "null has no properties", e.g. for "%2F.pdf"
      }
    }
  }
  return suggestedFilename || 'document.pdf';
}

So the majic needs to come from the URL via the reURI regexp.

What you need to do is this:

http://domain.com/path/to/Named.pdf
http://domain.com/path/to/your/api?fileId=123&saveName=Named.pdf

Each of these will result in a save as filename of Named.pdf thanks to the regexp code above.

Answer 2

Based on comments

You can add this to wherever you're using the viewer.js file.

setTimeout(() => {
  // Wait for PDFViewerApplication object to exist
  PDFViewerApplication.setTitleUsingUrl('custom-file.pdf');
}, 10);

Then when you download the PDF it will have that filename