How to disable external PDF viewer (acrobat.adobe.com/dc-chrome-extension) and use internal one again

[irs-mima1]

Hello,
I am using CefSharp to view datasheets in pdf format in my application. In the past the internal pdf extension was used, but now an external extension is loaded from adobe.com. The problem is, that I redirect all external URLs (except: chrome-extension://...) to the system browers. Another problem is, that many computers running my application are not connected to the internet.
How can I disable (or better remove) the external extension and use the internal classic one again?

The code used for external links:

public class CustomRequestHandler : RequestHandler
{
    protected override bool OnBeforeBrowse(IWebBrowser browserControl, IBrowser browser, IFrame frame, IRequest request, bool userGesture, bool isRedirect)
    {
        try
        {
            // Cancel navigation on external link and instead open them in system default browser
            return IsExternalLink(request.Url, true) || base.OnBeforeBrowse(browserControl, browser, frame, request, userGesture, isRedirect);
        }
        catch (Exception ex)
        {
            ex.ShowError();
            return true; // Cancel
        }
    }

    private static bool IsExternalLink(string url, bool openExternalUrl)
    {
        try
        {
            var uri = new Uri(url);

#if DEBUG
            Debug.WriteLine(uri);
#endif

            if (!uri.Host.Equals(LocalDomain) &&
                !uri.Host.EndsWith("." + LocalDomain) &&
                !uri.Scheme.Equals("chrome-extension") &&
                !uri.Scheme.Equals("chrome") &&
                !uri.Host.Equals("update.googleapis.com"))
            {
                if (openExternalUrl) Process.Start(url);
                return true;
            }
            else return false;
        }
        catch (UriFormatException)
        {
            if (openExternalUrl) Process.Start(url);
            return true;
        }
    }
}

[amaitland]

https://magpcss.org/ceforum/index.php is probably the best place to ask.