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):

const currentImgData = objsPool.get(objId);
          expect(currentImgData.width).toEqual(firstImgData.width);
          expect(currentImgData.height).toEqual(firstImgData.height);
          expect(currentImgData.kind).toEqual(firstImgData.kind);
          expect(currentImgData.data instanceof Uint8ClampedArray).toEqual(
            true
          );
          expect(
            currentImgData.data.every((value, index) => {
              return value === firstImgData.data[index];
            })
          ).toEqual(true);
        }
      }
      await loadingTask.destroy();
      firstImgData = null;
    });
  });
  describe("Multiple `getDocument` instances", function () {
    
    
    const pdf1 = buildGetDocumentParams("tracemonkey.pdf");
    
    const pdf2 = buildGetDocumentParams("TAMReview.pdf");
    
    const pdf3 = buildGetDocumentParams("issue6068.pdf");
    const loadingTasks = [];
    
    
    async function renderPDF(filename) {