Attach (recommended) or Link to PDF file here:
https://bitcoin.org/bitcoin.pdf

Configuration:
- Web browser and its version: all
- Operating system and its version: all
- PDF.js version: tested with 2.9.11, but most likely all versions
- Is a browser extension: no

Steps to reproduce the problem:
1. Type "a purely" (single space between "a" and "purely") - doesn't find anything
2. Type "a  purely" (two spaces between "a" and "purely") - finds the phrase

Sometimes even 3 spaces are necessary.

What is the expected behavior? (add screenshot)
![Screenshot from 2021-04-08 13-00-03](https://user-images.githubusercontent.com/6362989/114008903-57639a00-986b-11eb-903a-92bbebbd922b.png)

What went wrong? (add screenshot)
![Screenshot from 2021-04-08 13-01-53](https://user-images.githubusercontent.com/6362989/114008810-44e96080-986b-11eb-8232-f58a62ed7899.png)

This affects many PDFs because justify alignment is common enough.
function (data) {
          expect(data instanceof PasswordException).toEqual(true);
          expect(data.code).toEqual(PasswordResponses.INCORRECT_PASSWORD);
          return passwordIncorrectLoadingTask.destroy();
        }
      );
      const passwordAcceptedLoadingTask = getDocument(
        buildGetDocumentParams(filename, {
          password: "asdfasdf",
        })
      );
      expect(
        passwordAcceptedLoadingTask instanceof PDFDocumentLoadingTask
      ).toEqual(true);
      const result3 = passwordAcceptedLoadingTask.promise.then(function (data) {
        expect(data instanceof PDFDocumentProxy).toEqual(true);
        return passwordAcceptedLoadingTask.destroy();
      });
      await Promise.all([result1, result2, result3]);
    });
    it(
      "creates pdf doc from password protected PDF file and aborts/throws " +
        "in the onPassword callback (issue 7806)",
      async function () {
        const filename = "issue3371.pdf";
        const passwordNeededLoadingTask = getDocument(
          buildGetDocumentParams(filename)
        );
        expect(
          passwordNeededLoadingTask instanceof PDFDocumentLoadingTask