private void processRequest(RenderRequest renderRequest, PDDocument pdDocument,
                                Metadata metadata, ParseContext parseContext,
                                PageBasedRenderResults results) {
        if (renderRequest == PageRangeRequest.RENDER_ALL || renderRequest.equals(PageRangeRequest.RENDER_ALL)) {
            renderRange(pdDocument, 1, pdDocument.getNumberOfPages(),
                    metadata, parseContext, results);
        } else if (renderRequest instanceof PageRangeRequest) {
            int start = ((PageRangeRequest)renderRequest).getFrom();
            int toInclusive = ((PageRangeRequest)renderRequest).getTo();
            renderRange(pdDocument, start, toInclusive, metadata, parseContext, results);
        }
    }
This is the amount of time it takes for PDFBox/java to write the image after
it has been rendered into a BufferedImage.  Some formats take much longer
to encode than others.
tika-parsers/tika-parsers-standard/tika-parsers-standard-modules/tika-parser-pdf-module/src/main/java/org/apache/tika/renderer/pdf/pdfbox/PDFBoxRenderer.java