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.

data.actions["Mouse Up"] ||
          data.actions["Mouse Down"]) &&
        this.enableScripting &&
        this.hasJSActions
      ) {
        this._bindJSAction(link, data);
        isBound = true;
      }
      if (data.resetForm) {
        this._bindResetFormAction(link, data.resetForm);
        isBound = true;
      } else if (this.isTooltipOnly && !isBound) {
        this._bindLink(link, "");
        isBound = true;
      }
    }
    if (this.quadrilaterals) {
      return this._renderQuadrilaterals("linkAnnotation").map(
        (quadrilateral, index) => {
          const linkElement = index === 0 ? link : link.cloneNode();
          quadrilateral.append(linkElement);
          return quadrilateral;
        }
      );
    }
    this.container.className = "linkAnnotation";
    if (isBound) {
      this.container.append(link);
    }
    return this.container;