Attach (recommended) or Link to PDF file here:

Configuration:
- Web browser and its version: Version 81.0.4044.138 (Official Build) (32-bit)
- Operating system and its version: Windows 10
- PDF.js version: latest
- Is a browser extension: no

Steps to reproduce the problem:

1. Open https://mozilla.github.io/pdf.js/web/viewer.html
2. Open the provided document
3. ctrl + F  and search for 'costs' .
4. Search for 'costs' - match NOT found.
5. Click the 'Download' and open the file in Adobe Reader, and search for costs - match is found.

What is the expected behavior? (add screenshot)
The word 'costs' to be returned by search

What went wrong? (add screenshot)
No results found

Link to a viewer (if hosted on a site other than mozilla.github.io/pdf.js or as Firefox/Chrome extension):  https://mozilla.github.io/pdf.js/web/viewer.html
[2001_IESC_63_5_v6.pdf](https://github.com/mozilla/pdf.js/files/4644486/2001_IESC_63_5_v6.pdf)

Util,
} from "../shared/util.js";
/**
 * Text layer render parameters.
 *
 * @typedef {Object} TextLayerRenderParameters
 * @property {import("./api").TextContent} [textContent] - Text content to
 *   render (the object is returned by the page's `getTextContent` method).
 * @property {ReadableStream} [textContentStream] - Text content stream to
 *   render (the stream is returned by the page's `streamTextContent` method).
 * @property {HTMLElement} container - HTML element that will contain text runs.
 * @property {import("./display_utils").PageViewport} viewport - The target
 *   viewport to properly layout the text runs.
 * @property {Array<HTMLElement>} [textDivs] - HTML elements that are correspond
 *   to the text items of the textContent input. This is output and shall be
 *   initially be set to empty array.
 * @property {Array<string>} [textContentItemsStr] - Strings that correspond to
 *    the `str` property of the text items of textContent input. This is output
 *   and shall be initially be set to empty array.
 * @property {number} [timeout] - Delay in milliseconds before rendering of the
 *   text runs occurs.
 * @property {boolean} [enhanceTextSelection] - Whether to turn on the text
 *   selection enhancement.
 */
const MAX_TEXT_DIVS_TO_RENDER = 100000;
const DEFAULT_FONT_SIZE = 30;
const DEFAULT_FONT_ASCENT = 0.8;
const ascentCache = new Map();
const AllWhitespaceRegexp = /^\s+$/g;
function getAscent(fontFamily, ctx) {