no im trying to upload a pdf fileAre you trying to upload on your WP website ? If yes, then have a look your WP upload limit.
There are other third party websites that supports PDF uploads.Check the download section to see available supported websites.
no this is not a safe suggestion, who will really check the file checksum to make sure its same as virustotal, apart from that you need to download the file first them measure its checksum.If you are uploading it on BHW maybe use mega along with the virus total link.