Since the release of PDF.js 2.0.943 you can force URL to open in a new tab:
<script>
function applyConfig() {
PDFViewerApplication.preferences.set('externalLinkTarget', 2);
}
document.addEventListener('DOMContentLoaded', applyConfig, true);
</script>
Older versions we used:
PDFJS.externalLinkTarget = PDFJS.LinkTarget.BLANK;
This is also a hack that might work on newer versions but above script is best:
"externalLinkTarget": 2,
NOTE: Target lines in new PDF.js viewer.js & pdf.js looks like this:
target: item.newWindow ? _pdfjsLib.PDFJS.LinkTarget.BLANK : undefined
//target: _display_utils.LinkTarget.BLANK,
NEW VERSION is so much easier to use. Download the latest release at https://github.com/mozilla/pdf.js/releases
Change the line to: var _ui_utils = __webpack_require__(2);