Attach (recommended) or Link to PDF file here:
[Hong Kong Aircraft Engineering Company Limited_1511417616.1 2.pdf](https://github.com/mozilla/pdf.js/files/1539395/Hong.Kong.Aircraft.Engineering.Company.Limited_1511417616.1.2.pdf)


Configuration:
- Web browser and its version: Chrome: 63 
- Operating system and its version: windows and macOs
- PDF.js version: 2.0.185
- Is a browser extension: No

Steps to reproduce the problem:
1. Upload the above PDF and search for "article 1"
2. PDF.js showing only **2** match But actually **4** times available.   

What is the expected behavior? (add screenshot)

![screen shot 2017-12-07 at 7](https://user-images.githubusercontent.com/6101789/33720106-ed404576-db88-11e7-9c19-cf6aea74e9f3.png)



What went wrong? (add screenshot)

Link to a viewer (if hosted on a site other than mozilla.github.io/pdf.js or as Firefox/Chrome extension):

expect(outlineItemTwo.url).toEqual("http://google.com/");
      expect(outlineItemTwo.unsafeUrl).toEqual("http://google.com");
      expect(outlineItemTwo.newWindow).toBeUndefined();
      const outlineItemOne = outline[1];
      expect(outlineItemOne.bold).toEqual(false);
      expect(outlineItemOne.italic).toEqual(true);
      expect(outlineItemOne.color).toEqual(new Uint8ClampedArray([0, 0, 0]));
      await loadingTask.destroy();
    });
    it("gets non-existent permissions", async function () {
      const permissions = await pdfDocument.getPermissions();
      expect(permissions).toEqual(null);
    });
    it("gets permissions", async function () {
      
      const loadingTask0 = getDocument(
        buildGetDocumentParams("issue9972-1.pdf")
      );
      const promise0 = loadingTask0.promise.then(function (pdfDoc) {
        return pdfDoc.getPermissions();
      });
      
      const loadingTask1 = getDocument(
        buildGetDocumentParams("issue9972-2.pdf")
      );
      const promise1 = loadingTask1.promise.then(function (pdfDoc) {
        return pdfDoc.getPermissions();
      });
      
      const loadingTask2 = getDocument(