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):

buildGetDocumentParams("issue9972-3.pdf")
      );
      const promise2 = loadingTask2.promise.then(function (pdfDoc) {
        return pdfDoc.getPermissions();
      });
      const totalPermissionCount = Object.keys(PermissionFlag).length;
      const permissions = await Promise.all([promise0, promise1, promise2]);
      expect(permissions[0].length).toEqual(totalPermissionCount - 1);
      expect(
        permissions[0].includes(PermissionFlag.MODIFY_CONTENTS)
      ).toBeFalsy();
      expect(permissions[1].length).toEqual(totalPermissionCount - 2);
      expect(permissions[1].includes(PermissionFlag.PRINT)).toBeFalsy();
      expect(
        permissions[1].includes(PermissionFlag.PRINT_HIGH_QUALITY)
      ).toBeFalsy();
      expect(permissions[2].length).toEqual(totalPermissionCount - 1);
      expect(permissions[2].includes(PermissionFlag.COPY)).toBeFalsy();
      await Promise.all([
        loadingTask0.destroy(),
        loadingTask1.destroy(),
        loadingTask2.destroy(),
      ]);
    });
    it("gets metadata", async function () {
      const { info, metadata, contentDispositionFilename, contentLength } =
        await pdfDocument.getMetadata();
      expect(info.Title).toEqual("Basic API Test");
      
      expect(info.Custom).toEqual(undefined);