It would probably be:
$UpdateQuery->bindColumn("file_pdf", "s", "".($WA_DFP_UploadStatus["WA_UploadResult1"]["WA_UploadResult1_1"]["serverFileName"]) ."", "WA_IGNORE");
$UpdateQuery->bindColumn("file_doc", "s", "".($WA_DFP_UploadStatus["WA_UploadResult2"]["WA_UploadResult2_1"]["serverFileName"]) ."", "WA_IGNORE");
You can get the correct code from the bindings if you choose the file upload field and the "server file name" value.