Attach (recommended) or Link to PDF file [here:] Can't see how to attach a pdf here, but it is simple to create. Add a form object textbox to a pdf and make sure the option for "Multiline" is true.

Steps to reproduce the problem:
1.  Open a document with a Textbox that is set to Multiline.
2. Attempt to hit the Enter key to go to a new line.

What is the expected behavior? The cursor goes to a new line.

What went wrong? It does not go to a new line.

Link to a viewer: It can be reproduced on mozilla.github.io/pdf.js

I corrected the issue by altering the pdf.js file like this
element.addEventListener("keydown", event => { 
[...]
--} else if (event.key === "Enter") {
++ } else if (event.key === "Enter" && !this.data.multiLine) {

Our initial testing is coming through clean, and hopefully something like this code can be committed to the project in the future.

}
  /**
   * Render the quadrilaterals of the annotation.
   *
   * @private
   * @param {string} className
   * @memberof AnnotationElement
   * @returns {Array<HTMLElement>} An array of section elements.
   */
  _renderQuadrilaterals(className) {
    if (
      typeof PDFJSDev === "undefined" ||
      PDFJSDev.test("!PRODUCTION || TESTING")
    ) {
      assert(this.quadrilaterals, "Missing quadrilaterals during rendering");
    }
    for (const quadrilateral of this.quadrilaterals) {
      quadrilateral.className = className;
    }
    return this.quadrilaterals;
  }
  /**
   * Render the annotation's HTML element(s).
   *
   * @public
   * @memberof AnnotationElement
   * @returns {HTMLElement|Array<HTMLElement>} A section element or
   *   an array of section elements.
   */
  render() {