Hello

I have posted on nextcloud GIT this issue and they pointed me here.

Here is the issue I have posted - https://github.com/nextcloud/files_pdfviewer/issues/508

Configuration

Web browser and its version: Google Chrome, ver.94.0.4606.81 x64
Operating system and its version: Windows 10, 21H1, build 19043.1288
PDF.js version: v2.9.359
Is a browser extension: no I dont use it as extension

Steps to reproduce the problem:

What is the expected behavior?
Shared PDF created in AutoCAD without borders

![Snímek obrazovky 2021-10-19 120908](https://user-images.githubusercontent.com/11374526/137889425-c0983b5c-a557-46dc-ac32-d50c1dbb9ea9.png)

What went wrong?
Shared PDF created in AutoCAD is with border...
![image](https://user-images.githubusercontent.com/11374526/137888031-11852e03-41a4-48a0-bc0a-3ba0d65bd912.png)

Link to a viewer (if hosted on a site other than mozilla.github.io/pdf.js or as Firefox/Chrome extension):
https://cloud.ostritecky.cz/s/cryrqKarK9CEam8

PDF viewer rendering border around text and objects when creating files with AutoCAD and It looks really bad. Is there a way to switch it off ?

Testfile here:

[Test.pdf](https://github.com/mozilla/pdf.js/files/7372181/Test.pdf)

metrics = {
        width: 0.791 * fontSize,
        height: 0.705 * fontSize,
      };
      char = "\x6C";
    } else {
      unreachable(`_getDefaultCheckedAppearance - unsupported type: ${type}`);
    }
    
    const xShift = (width - metrics.width) / 2;
    const yShift = (height - metrics.height) / 2;
    const appearance = `q BT /PdfJsZaDb ${fontSize} Tf 0 g ${xShift} ${yShift} Td (${char}) Tj ET Q`;
    const appearanceStreamDict = new Dict(params.xref);
    appearanceStreamDict.set("FormType", 1);
    appearanceStreamDict.set("Subtype", Name.get("Form"));
    appearanceStreamDict.set("Type", Name.get("XObject"));
    appearanceStreamDict.set("BBox", bbox);
    appearanceStreamDict.set("Matrix", [1, 0, 0, 1, 0, 0]);
    appearanceStreamDict.set("Length", appearance.length);
    const resources = new Dict(params.xref);
    const font = new Dict(params.xref);
    font.set("PdfJsZaDb", this.fallbackFontDict);
    resources.set("Font", font);
    appearanceStreamDict.set("Resources", resources);
    this.checkedAppearance = new StringStream(appearance);
    this.checkedAppearance.dict = appearanceStreamDict;
    this._streams.push(this.checkedAppearance);
  }
  _processCheckBox(params) {