I have tried to download PDFs from certain URLs (e.g. https://example.com) using the Norconex Web Crawler (v3.0) and the configuration below but no luck. Can someone please help me with this?

<?xml version="1.0" encoding="UTF-8"?>
<httpcollector id="PDF Finder Config HTTP Collector">
    <workDir>./pdf-finder-output</workDir>
    <crawlers>
        <crawler id="PDF Finder">
            <startURLs stayOnDomain="true" includeSubdomains="true">
                <url>https://example.com</url>
            </startURLs>
            <maxDepth>-1</maxDepth>
            <sitemapResolver ignore="true" />
            <delay default="1000" />
            <documentFilters>
                <filter class="ExtensionReferenceFilter" onMatch="include">
                    PDF
                </filter>
            </documentFilters>
        </crawler>
    </crawlers>
</httpcollector>