Raster Translate to PDF format does not support multiy thread

When I use raster transaction tool to translate a TIFF file to PDF format, I just get a result raster that is part of source raster, not complated output. When I trun off configure GDAL_NUM_THREADS, the result is OK. So I guess the PDF driver does not support multithread, Don’t config GDAL_NUM_THREADS when convert to PDF format.