Unable to upload doc or PDF files

// Configuration information
"conference_brochure"=>array(
            "fields"=>array(
            "field_name"=>"conference_brochure",
                "configuration"=>array(
                    "upload_path"=>"./assets/company_site_images/",
                    "allowed_types"=>"gif|jpg|png|chm|doc|dcom|docx|dot|dotx|hwp|odt|pdf|pub|rtf|xps|key|odp|pps|ppsx|ppt|pptm|pptx|PDF|DOC|XML|DOCX",
                    "file_ext_tolower"=>"TRUE",
                    "overwrite"=>"TRUE",
                    "max_size"=>"5120"
                )
            )
        ),


I have tried various combinations of MIME types with no success. 
I am able to upload images.
Codeigniter 3 on PHP 7.
Thanks for the help.